The Theme-o-rama module was originally made by using the code for the "switch theme" module, and including a set list of theme choices rather than whatever is listed in the styles/ directory.
But due to a recent change in the switch-themes code, the old Theme-o-rama stopped working when I updated it to include the Tikipedia choice. I hope I'll be able to figure out a Theme-o-rama script that doesn't get stripped out of the module by Tiki. In the meantime, Theme-o-rama is a "fake module," actually a module-lookalike template file (Javascript OK), called from tiki.tpl.
This increases admin work, since every tiki.tpl file — default and theme-specific — has to be edited to include the file. And it's anti-Tiki in the sense that things that look like modules should be modules, configurable through Tiki's web interface. But modules' inability to contain things like onchange="this.form.submit();" makes this impossible, unless I'm missing something.
UPDATE: I made and uploaded a .php-and-.tpl module that contains the script, so it works, not having to go through the user modules processing.
-- Gary