If you're running Microsoft App-V in a traditional App-V Server-based infrastructure, desktop configuration is controlled by an App-V Management Server. Depending on local client configuration and provider policy, client will periodically refresh its configuration against server. This once called "DC Refresh" now referred as "Publishing Refresh," during it, App-V client receives list of apps to be published (APPLIST.XML) and from this'll "cache icons" and OSD files by retrieving them from locations specified in APPLIST.XML received from server. Locations of OSD and Icons can come directly from locations specified in APPLIST.XML data or they can come from the use of OSDSourceRoot and IconSourceRoot registry values which allow client computer to receive its ICO and OSD files from an alternate location. App-V client then creates appropriate shortcuts and registers file type associations based on information generated by App-V Server. More info here.
"Sometimes problems will occur during "publishing" portion of publishing refresh. When you refresh, you mayn't get any errors but you still mayn't have entire app configuration you would expect. This's an issue we see every now and then from customers where they ask "refresh is succeeding but where're all my icons?"," explains Microsoft.
More Info: where are my icons? Troubleshooting