If you are still using Tiger and you want a cool way to spruce up the design of your Mac then you can use Shape Shifter. After searching around on the internet I have come across a really cool source for finding shape shifter themes. If you head over to Interfacelift, you can check out all of there designs.

The designs vary in quality, but if you search through them all you can usually find some theme that can make your Mac stand out. If you have shape shifter installed and you want a new source of themes interface lift is definitely a site to check out.