An application to make my Mac UI look different?

So originally I was just going to download and install Lion but because of the hefty number of negative reviews and incompatible essential (to me) applications I think I'll pass.

However I got myself sort of excited about having a change in my mac UI with Lion so now I'm looking for a program to change my MacBook Pro's theme around.

I'm not looking for anything crazy (unless that's possible) I just feel like having a change of colors or something. I have an app that changes the docks color and allows you to use a screensaver as a wallpaper and I know how to change application icons so I don't need any of that. I was sort of looking for something that would allow me to be able to change the color of menus,windows and other things like such.

Any advice would be appreciated .

Seriously, my advice is don't mess with it. Yeah, that's not what you want. So take the advice of others to follow, but you've been warned.

Yeah I'd be reluctant to mess with those things as well.