To my knowledge, when using Teamviewer it disables windows aero. I know LogMeIn does and I think Teamviewer does the same. When I use LogMeIn I just get a black desktop background because I normally have a slideshow. The slideshow is part of aero which means it is disabled when aero is switched off.
Try refreshing the laptops Windows Experience Index score as if that has not been run, aero will not run. Also, try setting the background to a solid colour like red to see if that works. If the PC is nto powerful enough to run aero, you will need to use a non aero theme.
Hope this helps