Add attribute data-icon to <option> items with the name of font awesome css class name.
<select data-placeholder="Choose a Project..." class="icon-select" style="width:350px;"
tabindex="2">
<option data-icon="fa-download">Project A</option>
<option data-icon="fa-cloud">Project B</option>
<option data-icon="fa-fighter-jet">Project C</option>
</select>
Use chosenIcon() in place of chosen() passing in the same properties:
$(".icon-select").chosenIcon({
disable_search_threshold: 10
});
All properties of chosen() are available through chosenIcon()