Does the front page show 5 random cards in Multiverse, or 5 cards at random from 5 random sets? If it's the former, then people who put in the work and make a lot of cards would get the bump. If it's the latter, however, the focus gets shifted to the large number of people who made 10 or less cards, then flew away. Kind of reminds me of the big state vs. little state problem we had/have when writing the U.S. Constitution. Except, in this situation, I'd think that we'd prefer to favor those who did the work...

Ooh, interesting. Particularly given the somewhat unclear definition of "completed". I do see the problem, but I'm not quite sure what to do about it. Perhaps on the front page I could list the number of cardsets, but also say "of which [29] have more than 150 cards", or "have their target number of cards" (deduced from the skeleton).

Well, you could just have a way for the owner to flag a set as done?

I don't know how many sets would ever be considered done, then. All my slots are filled for Magic 20XD6. I still have occasional flavor text, testing and maybe images to put in. I don't ever think I'll be 'done'. I would assume that applies to many people.