Own experience with celebs:
Never converted them from a gallery or free site.
However I have a blog devoted to celeb only content and it stands alone as I now don't bother to make gallaries etc. It converts ok.Few sales per month I just post on it and leave it alone. It's fairly softcore.
After trying for a while, I found it best to market it less as porn, more as a celeb news/gossip site.
Hope this helps