I think that it would speed up theme voting process if theme makers would made 1:1 theme template of whole theme. It would also attract people in trying themes. Market your theme! I do not know what applications theme makers use but i would appreciate if this kind "sprite" template if it is possible.

And i have to say that i just tried ~4 themes and i wasn't too happy on quality. Only one seemed to be balanced on colors and text readability. But that´s just me and rather pedantic and strict taste.

.edit
So please. Do not make them just applying some color changes to one you have already made. Design them from bottom up.