When I use a static resource for my jquery ui, the icons are not loading, if I use the cdn links, it loads properly.
Here I referenced the css and js for jqueryui but I think the problem is that the css code in jquery-ui.theme.min.css is unable to find the path the image which actually exists on the static resource.
<apex:includeScript value="{!URLFOR($Resource.jQuery321)}"/>
<apex:includeScript value="{!URLFOR($Resource.jqueryui112,'/jquery-ui-1.12.1.custom/jquery-ui.min.js')}"/>
<apex:stylesheet value="{!URLFOR($Resource.jqueryui112,'/jquery-ui-1.12.1.custom/jquery-ui.min.css')}"/>
<apex:stylesheet value="{!URLFOR($Resource.jqueryui112,'/jquery-ui-1.12.1.custom/jquery-ui.structure.min.css')}"/>
<apex:stylesheet value="{!URLFOR($Resource.jqueryui112,'/jquery-ui-1.12.1.custom/jquery-ui.theme.min.css')}"/>
.ui-button .ui-icon { background-image: url({!URLFOR($Resource.jqueryui112,'/jquery-ui-1.12.1.custom/images/')}ui-icons_777777_256x240.png) }
URLFOR
only works VF page . try to include this in VF page then it might work.