For something more personal or unusual:
http://www.wincustomize.com/
The 2nd row shows the categories of add-ons you can chose:
Window Blinds / Object Dock / Icon Packager / Wall Papers / Deskcapes
It's always a good idea to plan things out carefully so it all 'works together' and looks good.
And you don't want to slow down your system too much by adding resource intensive tasks and gadgets.