I have looked at and tried installing one of the WPMU themes on several of my sites (even a new one), but just cannot see how the they work. The main one I have tried is Fixer.
I can log in, I can do certain things, like add text - though it seems to go everywhere except where I need it to, but I just cannot replicate the style that I see on the promotional pages for the themes.
Are the graphics included? How are new backgrounds added?
Is there a tutorial that goes through each stage anywhere?
Sorry to be a pain. I use and love most of the plugins and my usual theme framework (Headway) looks as if it's in trouble financially.