It may be possible by changing your icons for something normal. Or ricing the hell out of your desktop in such a way that it doesn’t look like anything immediately recognizable. In both cases, see:
- general styling discussion - here people converse on what (and often how) they do styling
- change background color of your icons - starting from here, you can learn how to edit icons
- You also can make your window borders less apparent with this guide
Another option is to hide the panel itself, either with auto-hide in panel preferences or completely removing all panels and using hotkeys and terminal to do everything.
In any case, keep in mind that even if you can masquerade visually, Qubes is not trying to hide at all. It should be very detectable by the way it uses network and pretty much obvious is case someone has access to filesystem of your qube.