I think it would be very useful if users could design their own chess sets. In my case, I have in mind a design that would make me a lot more concentrated when playing. ChessCube would be more popular if people could make designs of chess sets and submit them for consideration, or at least have the possibility of making chess sets for their own use exclusively.
As I unlocked several chess sets, when I started using a particular one that I liked, I noticed instant, radical improvements in my playing. Therefore, if people could create chess sets that have the chance to become available for the general public on ChessCube, the chances for more passionate playing would increase dramatically because the more chess sets ChessCube has, the more chances people have to find a particular one that they will love.
This would give ChessCube a new dimesnion of fun. Further than the fun we have when we use our reason in a chess game we would also have artistic fun.
I trust ChessCube's innovative side and I am sure that it is very aware of the importance of adding this feature, so I know that it's only a matter of time. However, more than obviously I posted this because I want this as sooon as possible!! So far I used to play 10-20 games a week. With a feature like this I would play at least 100!