Simple question - How do I get thumbnails to show on everything BUT folders?

I'm trying to get it to where thumbnails don't show on folders by default, but they do show when they're just the files (gifs, pics, etc). I basically want my folders to look nice and uniform, but when I open them up I wanna be able to preview the files as normal.

Is this possible? Googling didn't help much.

Win7 btw.