I've been toying with the idea of starting another blog filled with just PNGs for photoshopping. What's great about the PNG format is that you can have a transparent background. You can then just copy and paste them over whatever comes into your head. The original picture will peek through the transparent parts.
Like here for instance. I just happened to have a picture of our (Yes we CAN!) President on the desktop so I thought I'd see if he'd fit behind a PNG I'd made of someone behind bars. And bazinga! he fit just perfectly. What a silly idea. I'm like that sometimes. Silly, silly, silly, and in no way deserving of an audit.
***Update: So here's the behind-bars PNG that I made:
See? And you could put it over any image with a dark background. I searched my HD for images with a dark background and only found one other: