css - programmatic p:stack not loading image -

i creating primefaces stack (works <p:menu>) follows:

<p:stack icon="resources/images/stack.png" expanded="true" model="#{viewcartmanagedbean.model}"> 

this line above in html page. programmed model in jsf managed bean:

model = new defaultmenumodel (); defaultmenuitem item = new defaultmenuitem("x"+q); item.seticon("xlogo"); model.addelement(item); 

where variable model private field of managed bean private menumodel model;

finally make icon 1 own image, wrote in css file:

.xlogo { background-image:url(../resources/images/cart.png) !important; } 

and works fine except icon image not loaded ("xlogo") can see here:

can me? have problems customizing own icon in primefaces.