My rule of thumb: Never have as a desktop background anything that would make a girl, who has come into my bedroom where the computer is, think twice about her decision to come in.
That means no gaming, geek, or other stuff like that. So I've got a Windows 7 standard image---there's mountains and big blocks of ice and the sun setting over the horizon.
On my laptop? A picture of Screwy Squirrel, because if she's using my laptop, chances are good she already knows how playfully screwy I am, so a cartoon picture---while she's on my bed naked, most likely---fits.
