We’ve had a couple users have problems with their finder icons not showing up. Where the icons would be, all they see is white space but when they hover over it, they get the alt text. They’re using IE 11 and in the compatibility view settings, we have users uncheck the box that says “Display intranet sites in compatibility view”. Is the icon images not showing potentially an issue within the browser settings? 
I doubt browser setting is an issue. If the issue is only for handful of users and not for all, we can try and clear browser cache to see whether it help. Also may I know the CM1 version in which the users are experiencing this issue?
The version we have is Version 5.2.5 Build 201511R20 (0)
We couldn’t reproduce the issue. Could be for some reason IE is loading in other than IE11 mode like IE8. You could use IE developer tools - Emulation (F12 key can load it) and change the mode to different versions of IE to see whether it makes any difference. A support ticket would be helpful if needs help from Percussion support team.