This is a small thing, but I think the themeswitcher plugin would benefit from being allowed to select which themes you want to list.

Y'know just in case you don't want to delete the default themes or if you want to beta test your own theme without making it public.

Sounds reasonable. The testing of themes is exactly what the plugin was intended to do. But for beta testing wouldn't you want the selector not to show at all except for whomever should be testing?

I'm open to suggestions on how that might be specified.

Well, you can have unpublished pages still visible for the administrator, couldn't there be a similar system for themes?

I would favor a simple selector like with the languages maybe.

Check out the development build for enhancements in this area.