what you need
[li]create a folder in the root of your SD card named wtheme sd:\wtheme[/li][li]copy the contents of the theme folder to the wtheme folder[/li][/ul]
saving more than one theme to your sd card
[li]move the theme folder to your sd card wtheme folder sd:\wtheme hemename[/li][li]switch themes from USB Loader GX settings, the default password is ab121b[/li][/ul]
the default theme for USB Loader GX is a wii menu look-a-like.
this site is the the official theme database, some pretty cool stuff.
here is the one im currently using its called Monkey Man