We can configure to read the leaf nodes icon from the database. For this purpose we need to set the icon field in table configuration
<?php 
require_once '../../../php/demo/tabs.php';
?>
<!DOCTYPE html>
<html>
  <head>
    <title>Guriddo TreeGrid PHP Demo</title>
    <link rel="stylesheet" type="text/css" media="screen" href="../../../css/jquery-ui.css" />
    <link rel="stylesheet" type="text/css" media="screen" href="../../../css/trirand/ui.jqgrid.css" />
    <style type="text">
        html, body {
        margin: 0;            /* Remove body margin/padding */
        padding: 0;
        overflow: hidden;    /* Remove scroll bars on browser window */
        font-size: 75%;
        }
        
    </style>
    <script src="../../../js/jquery.min.js" type="text/javascript"></script>
    <script src="../../../js/trirand/i18n/grid.locale-en.js" type="text/javascript"></script>
    <script src="../../../js/jquery-ui.min.js" type="text/javascript"></script>
     <script src="../../../js/trirand/jquery.jqGrid.min.js" type="text/javascript"></script> 
    <script type="text/javascript">         
        $.jgrid.no_legacy_api = true;
        $.jgrid.useJSON = true;
        $.jgrid.defaults.width = "700";
    </script>
  </head>
  <body>
      <div>
          <?php include ("treegrid.php");?>
      </div>
      <br/>
      <?php tabs(array("treegrid.php"));?>
   </body>
</html>
treegrid.php.
<?php
ini_set("display_errors",1);
require_once '../jq-config.php';
// include the driver class
require_once ABSPATH."php/PHPSuito/DBdrivers/jqGridPdo.php";
// include the jqGrid Class
require_once ABSPATH."php/PHPSuito/jqTreeGrid.php";



// Connection to the server
$conn = new PDO(DB_DSN,DB_USER,DB_PASSWORD);
// Tell the db that we use utf-8
$conn->query("SET NAMES utf8");
// Create the jqTreeGrid instance
$tree = new jqTreeGrid($conn);

$tree->SelectCommand = "SELECT * FROM nested_category";

// set the table and primary key
$tree->table = 'nested_category';
$tree->setPrimaryKeyId('category_id');
// set tree model and table configuration
$tree->setTreeModel('nested');
// set the icon db field for the leaf nodes.
$tree->setTableConfig(array('id'=>'category_id', 'left'=>'lft', 'right'=>'rgt', 'icon'=>'uiicon'));

// autoloading nodes
$tree->autoLoadNodes = true;
// show any error (if any ) from server
$tree->showError = true;

$tree->setColModel();

$tree->setUrl('treegrid.php');
$tree->dataType = 'json';
// Some nice setting
$tree->setColProperty('name',array("label"=>"Name", "width"=>170));
$tree->setColProperty('price',array("label"=>"Price", "width"=>90, "align"=>"right"));
$tree->setColProperty('qty_onhand',array("label"=>"Qty", "width"=>90, "align"=>"right"));
$tree->setColProperty('color',array("label"=>"Color", "width"=>100));

// hide the not needed fields
$tree->setColProperty('category_id',array("hidden"=>true,"index"=>"accounts.account_id", "width"=>50));
$tree->setColProperty('lft',array("hidden"=>true));
$tree->setColProperty('rgt',array("hidden"=>true));
$tree->setColProperty('level',array("hidden"=>true));
$tree->setColProperty('uiicon',array("hidden"=>true));

// and finaly set the expand column and height to auto
$tree->setGridOptions(array(
    "ExpandColumn"=>"name",
    "height"=>"auto",
    "sortname"=>"account_id"
    ));

$tree->renderTree('#tree', '#pager', true,null, null, true, true);