You can set the ImageUrl property to the URL of images that will show before the item text in a dropdownlist structure.
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="default.aspx.cs" Inherits="JQSuiteASPNETExample.examples.combobox.clientevents._default" %>
<%@ Register Assembly="Trirand.Web" TagPrefix="trirand" Namespace="Trirand.Web.UI.WebControls" %>

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
    <title>jqComboBox for ASP.NET WebForms - Text and Images</title>
    <!-- The jQuery UI theme that will be used by the combobox  -->
    <link rel="stylesheet" type="text/css" href="http://ajax.aspnetcdn.com/ajax/jquery.ui/1.10.3/themes/redmond/jquery-ui.css" />    
    <!-- The jQuery UI theme extension the combobox needs -->
    <link rel="stylesheet" type="text/css" href="/themes/ui.jqcombobox.css" />
    <!-- jQuery runtime minified -->
    <script type="text/javascript" src="http://ajax.microsoft.com/ajax/jquery/jquery-2.0.3.min.js"></script>
    <!-- The jqComboBox client-side javascript -->
    <script type="text/javascript" src="/js/trirand/jquery.jqcombobox.min.js"></script>
    <style type="text/css">    
        body, html { font-size: 80%; }
    </style>
</head>
<body>    
    <form id="Form1" runat="server">
    <table cellpadding="10" cellspacing="10">
        <tr>
            <td valign="top">
                <trirand:JQComboBox 
                    ID="JQComboBox1"
                    Height="200"
                    Width="150"                    
                    runat="server">
                     <Items>
                        <trirand:JQListItem Text="One" Value="One" />
                        <trirand:JQListItem Text="Two" Value="Two" />
                        <trirand:JQListItem Text="Three" Value="Three" />
                        <trirand:JQListItem Text="Four" />
                        <trirand:JQListItem Text="Five" />
                        <trirand:JQListItem Text="Six" />
                        <trirand:JQListItem Text="Seven" />
                        <trirand:JQListItem Text="Eight" />
                        <trirand:JQListItem Text="Nine" />
                        <trirand:JQListItem Text="Ten" />
                    </Items>
                    <ClientSideEvents
                        Show="handleShow"
                        Hide="handleHide"
                        MouseOver="handleMouseOver"
                        MouseOut="handleMouseOut"
                        Select="handleSelect"
                        Initialized="handleInitialized"
                        KeyDown="handleKeyDown"                                           
                    />
                </trirand:JQComboBox>
            </td>  
            <td valign="top" style="width:300px; height: 300px;">                
                <div id="eventLog" style="height:300px; overflow:auto; font-size:110%; font-family:Tahoma" />
            </td>         
        </tr>
    </table>   
    
    <br /><br /><br />
    <br /><br /><br />
    <script type="text/javascript">

        function handleInitialized(dropDown) {
            write("ComboBox initialized.");
        }

        function handleKeyDown(dropDown, events) {
            write(events.keyCode + " is the keyCode of the key pressed.");
        }

        function handleShow() {
            write("ComboBox shown.");
        }

        function handleHide() {
            write("ComboBox hidden.");
        }

        function handleMouseOut(item, event) {
            var comboBox = $("#<%= JQComboBox1.ClientID %>").getComboBoxInstance();
            var itemOptions = comboBox.getItemOptions(item);

            writeLine(itemOptions.text, "<b>MouseOut</b> fired");
        }

        function handleMouseOver(item, event) {
            var comboBox = $("#<%= JQComboBox1.ClientID %>").getComboBoxInstance();
            var itemOptions = comboBox.getItemOptions(item);

            writeLine(itemOptions.text, "<b>MouseOver</b> fired");
        }

        function handleSelect(item, event) {
            var comboBox = $("#<%= JQComboBox1.ClientID %>").getComboBoxInstance();
            var itemOptions = comboBox.getItemOptions(item);

            if (itemOptions.text == "Two") {
                writeLine(itemOptions.text, " : <b>cannot be selected</b>");
                return false;
            }

            writeLine(itemOptions.text, " : <b>Select</b> fired");
        }

        function writeLine(itemText, message) {
            var currentText = $("#eventLog").html();
            $("#eventLog").html(message + " for item <b>" + itemText + "</b><br>" + currentText);
        }

        function write(message) {
            var currentText = $("#eventLog").html();
            $("#eventLog").html("<b>" + message + "</b><br>" + currentText);
        }

    </script>     
    
    <div>
        <trirand:codetabs runat="server" ID="tabs"></trirand:codetabs>
    </div>
    
    </form>
</body>
</html>
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace JQSuiteASPNETExample.examples.combobox.clientevents
{
    public partial class _default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

        }
    }
}
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" />