Well this is supposed to be a 'general discussion' forum about skinning so it seems the best place to put this opinion post.
Lately I've been agog over the eye-catching/wrenching wallpapers people post when they upload a WB skin. Now, don't get me wrong, many of them are beautiful; that said, the point of a WB skin is to skin the window, not view the wallpaper.
I don't know about y'all, but 99% of the time, I'm in a window doing something; I don't have time to just sit and stare at wallpaper.
Ergo, it seems to me that if you really, really, really want to build a 'master' or a 'killer' skin - try doing it on a desktop where you have the background simply set to a color - say gray.
If you look at the skin then; against a blank back drop and you can say "wow, what a skin!" then you probably have the makings of a master/killer skin. But, if you have to have your wallpaper visible to 'show off' your skin, then do you really have a great skin?
Just my $.02. My favorite skins thus far; aero frost, aero midnight and naked.
randyv