If one of the predefined cell formatters (integer, link, email, number, currency, checkbox) is not suitable in your scenario, you can use custom formatters.

With custom formatters you can define your own javascript client-side format and unformat functions. Format function are used to display the cell and unformat is used to unformat the cell in display mode and show it in edit mode
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using Trirand.Web.Mvc;
using System.Web.UI.WebControls;

namespace MVCDemo.Models
{
    public class CustomFormattersJqGridModel
    {
        public JQGrid EmployeesGrid { get; set; }

        public CustomFormattersJqGridModel()
        {
            EmployeesGrid = new JQGrid
                             {
                                 Columns = new List<JQGridColumn>()
                                 {
                                     new JQGridColumn { DataField = "ID", 
                                                        Width = 50 },
                                     new JQGridColumn { DataField = "PhotoFileName",                                                         
                                                        Width = 100
                                                      },
                                     new JQGridColumn { DataField = "Photo",                                                         
                                                        Width = 100
                                                      },
                                      new JQGridColumn { DataField = "Rating",
                                                         Width = 100
                                                      }
                                                         
                                 },
                                 Width = Unit.Pixel(400),
                                 Height = Unit.Pixel(350)
                             };
            
        }
    }
}
@model MVCDemo.Models.CustomFormattersJqGridModel
@using Trirand.Web.Mvc
@using MVCDemo.Models

<!DOCTYPE html>
<html lang="en-us">
<head>
    <meta charset="utf-8">
    <title>jqGrid for ASP.NET MVC - Custom Cell Formatters</title>    
    <!-- jQuery runtime minified -->
    <script src="~/Scripts/jquery-3.2.1.min.js" type="text/javascript"></script>
    <!-- The jqGrid localization file we need, English in this case -->
    <script type="text/javascript" src="~/Scripts/trirand/i18n/grid.locale-en.js"></script>
    <!-- The jqGrid client-side javascript -->
    <script type="text/javascript" src="~/Scripts/trirand/jquery.jqGrid.min.js"></script>
    <!-- The jQuery UI theme that will be used by the grid. -->
    <link rel="stylesheet" type="text/css" href="http://code.jquery.com/ui/1.12.1/themes/redmond/jquery-ui.css" />
    <!-- The jQuery UI theme extension jqGrid needs -->    
    <link rel="stylesheet" type="text/css" href="~/Content/themes/ui.jqgrid.css" />
</head>
<body>    
    <div>                   
        @Html.Trirand().JQGrid(Model.EmployeesGrid, "JQGrid1")
    </div>
    <br /><br />
    <div>
                  
    </div>
    
    <script type="text/javascript">
        // The FormatFunction for CustomFormatter gets three parameters           
        // cellValue - the original value of the cell
        // options - as set of options, e.g
        //   options.rowId - the primary key of the row
        //   options.colModel - colModel of the column
        // rowData - array of cell data for the row, so you can access other cells in the row if needed

        function formatImage(cellValue, options, rowObject) {            
            var imageHtml = "<img src='../Content/CustomFormattersImages/" + cellValue + "' originalValue='" + cellValue + "' />";
            return imageHtml;
        }

        // The FormatFunction for CustomFormatter gets three parameters           
        // cellValue - the original value of the cell
        // options - as set of options, e.g
        //   options.rowId - the primary key of the row
        //   options.colModel - colModel of the column
        // cellObject - the HMTL of the cell (td) holding the actual value
        function unformatImage(cellValue, options, cellObject) {
            return $(cellObject.html()).attr("originalValue");
        }

        function formatRating(cellValue, options, rowObject) {
            var color = (parseInt(cellValue) > 0) ? "green" : "red";
            var cellHtml = "<span style='color:" + color + "' originalValue='" +
                                    cellValue + "'>" + cellValue + "</span>";

            return cellHtml;
        }

        function unformatRating(cellValue, options, cellObject) {
            return $(cellObject.html()).attr("originalValue");
        }
       </script>
    
</body>
</html>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using MVCDemo.Models;
using Trirand.Web.Mvc;

namespace MVCDemo.Controllers.Grid
{
    public partial class GridController : Controller
    {
        public class Employee
        {
            public int ID { get; set; }
            public string PhotoFileName { get; set; }
            public string Photo { get; set; }
            public int Rating { get; set; }
        }

        public List<Employee> GetEmployeesData()
        {
            List<Employee> list = new List<Employee>();
            list.Add(new Employee { ID = 1, Photo = "1.jpg", PhotoFileName = "1.jpg", Rating = 20 });
            list.Add(new Employee { ID = 2, Photo = "2.jpg", PhotoFileName = "2.jpg", Rating = -10 });
            list.Add(new Employee { ID = 3, Photo = "3.jpg", PhotoFileName = "3.jpg", Rating = 30 });
            list.Add(new Employee { ID = 4, Photo = "4.jpg", PhotoFileName = "4.jpg", Rating = 50 });
            list.Add(new Employee { ID = 5, Photo = "5.jpg", PhotoFileName = "5.jpg", Rating = -40 });
            list.Add(new Employee { ID = 6, Photo = "6.jpg", PhotoFileName = "6.jpg", Rating = -60 });
            list.Add(new Employee { ID = 7, Photo = "7.jpg", PhotoFileName = "7.jpg", Rating = 10 });
            list.Add(new Employee { ID = 8, Photo = "8.jpg", PhotoFileName = "8.jpg", Rating = 40 });
            list.Add(new Employee { ID = 9, Photo = "9.jpg", PhotoFileName = "9.jpg", Rating = -20 });

            return list;
        }

        public ActionResult FunctionalityCustomFormatters()
        {            
            // Pass the custmomized grid model to the View
            return View(GetCustomFormattersGridModel());
        }

        // This method is called when the grid requests data. You can choose any method to call
        // by setting the JQGrid.DataUrl property
        public JsonResult CustomFormattersDataRequested()
        {
            // Get both the grid Model and the data Model
            // The data model in our case is an autogenerated linq2sql database based on Northwind.
            var gridModel = GetCustomFormattersGridModel();

            // return the result of the DataBind method, passing the datasource as a parameter
            // jqGrid for ASP.NET MVC automatically takes care of paging, sorting, filtering/searching, etc
            return gridModel.EmployeesGrid.DataBind(GetEmployeesData().AsQueryable());
        }

        private CustomFormattersJqGridModel GetCustomFormattersGridModel()
        {
            // Get the model (setup) of the grid defined in the /Models folder.
            var gridModel = new CustomFormattersJqGridModel();
            var grid = gridModel.EmployeesGrid;

            // Customize/change some of the default settings for this model
            // ID is a mandatory field. Must by unique if you have several grids on one page.
            grid.ID = "OrdersGrid";
            // Setting the DataUrl to an action (method) in the controller is required.
            // This action will return the data needed by the grid
            grid.DataUrl = Url.Action("CustomFormattersDataRequested");
            grid.Columns.Find(c => c.DataField == "Photo").Formatter = new CustomFormatter
                                                                    {
                                                                        FormatFunction = "formatImage",
                                                                        UnFormatFunction = "unformatImage"
                                                                    };
            grid.Columns.Find(c => c.DataField == "Rating").Formatter = new CustomFormatter
                                                                    {
                                                                        FormatFunction = "formatRating",
                                                                        UnFormatFunction = "unformatRating"
                                                                    };

            return gridModel;
        }
    }
}
Switch theme:


Theming is based on the very popular jQuery ThemeRoller standard. This is the same theming mechanism used by jQuery UI and is now a de-facto standard for jQuery based components. The benefits of using ThemeRoller are huge. We can offer a big set of ready to use themes created by professional designers, including Windows-like themes (Redmond), Apple-like theme (Cupertino), etc. In addition to that any jQuery UI controls on the same page will pick the same theme.

Last, but not least, you can always roll your own ThemeRoller theme, using the superb Theme Editor

To use a theme, simply reference 2 Css files in your Html <head> section - the ThemeRoller theme you wish to use, and the jqGrid own ThemeRoller Css file. For example (Redmond theme):

<link rel="stylesheet" type="text/css" media="screen" href="/themes/redmond/jquery-ui-1.8.2.custom.css" />
<link rel="stylesheet" type="text/css" media="screen" href="/themes/ui.jqgrid.css" />