At home all the systems have the Debian default artwork which is usually abstract and subtle. I don't use icons, and I full screen most programs, so I mostly don't see it most of the time anyway. At work I put up with whatever the client wants, though if I can get rid of their default and just have a solid black background then that's what I do.

Corporate logos are all good and well, but if you can't work out what the icons are then it's not much use... At one firm I worked for, the security team didn't want branding to be visible as they thought it was a risk, but marketing wanted it on everything, and so our badges and laptops all sported corporate logos....