Adding iTerm2 Themes
Not available yet in the Alpha downloads but supposedly available soon when Alpha 17 is released, iTerm2 provides support for theming your terminal window. You can take advantage of this now by downloading an iTerm2 nightly build (or wait for Alpha 17) but adding these custom themes in iTerm2 is fairly easy.
Update - March 3, 2011: iTerm2 Alpha 17, adding theme support among other things, has been released.
A new preference window in an iTerm2 nightly build, which presumably will show up in Alpha 17 when released, replaces Bookmarks with an Address Book:
Under the Colors section of the Address Book preference window, there is a drop-down box labeled Load Presets.... Click on this drop-down, then click the Import... command in order to import the theme you'd like to import.
There is also an iTerm2 Color Gallery with a small but growing collection of user-contributed themes you can use to get started, if you don't want to create your own right away. My favorite presently, which also happens to be my favorite VIM theme as well, is Solarized.