The delete icon in jTable (jQuery, not java) is set with CSS. See for example the jtable_basic.css file which is containing the following lines:
div.jtable-main-container table.jtable tbody > tr > td .jtable-delete-command-button {
background: url('delete.png') no-repeat;
width: 16px;
height: 16px;
}
So change the background in the css file you use for your jTable.