Did not think your complaining.
Just answering your question why custom stylesheets you buy dont fit automatically. Basically if you use a stylesheet with relative url's meaning not the full url to the image photopost is going to look for those images in the photopost directory. Everything vbulletin is coded using relative url's meaning they expect everything to exist in that directory. Hense you need to modify the paths to full url to use over an external program like Photopost.