If you’re running a lightweight window manager then chances are you might also be interested in using a lightweight desktop manager as well.
x11-misc/slim is a super light desktop manager for running whatever WM you decide to go with, in my case evilwm. It comes with a variety of themes (available in package form via x11-themes/slim-themes) which are very nice.
Behold my Evangelion based theme, Nerv! Sexify your slim today!
To install and use the theme download and untar. You should have the directory nerv/ with three files. Move this directory into the themes directory (generally /usr/share/slim/themes). Now edit your /etc/slim.conf file and edit the following line:
current_theme nerv
Done!
nerv theme screen