If you're looking to brighten up your mobile a little then you might want to think about installing Abstract Love.
The Abstract Love theme transforms several aspects of the S60 interface to make it a better place to be. For starters, it adds a cool vector-based flower design as a background image to the main screen. The design itself looks great, but unfortunately it's watermarked and renders some of the black text unreadable.
Hop into the S60 menu system and you'll encounter a different background again. This time Abstract Love goes with a green, flowery background and applies some nice flower icons to the menu. Again, there are some issues with text readability, but on the whole the design is pretty striking.
The artwork within Abstract Love is very impressive, although the way the various elements hang together needs a little work.