Sorry, I don't know about basic themes. I only play with my owns which are always big monsters... but if you want to build your own, I don't recommend to modify an existing one. Just start from scratch with little things:
- desktop2 or jdesk
- few hotkeys (file manager, step.rc, gfx editor,...)
- systray (no settings needed; just load the module, at first)
- popup (only the main popup definitions)

Configuring Litestep is very easy. All you have to do is to read the docs and make some tests... Optionaly, you'll need some artistic capabilities...