Thanks for your suggestion. As I remenber, sometimes I have developed something like this for another customer, so I could resell the solution to you if you need this badly. Whatever I have in mind regarding the "feature" itself, it is standing out of the miniBB concepts and never be added by default. MiniBB concentrates on the content, as the content is the only thing which would allow to earn most of forum owners. All other things like extended profiles or styling are up to each certain audience and it is a question of customized codes. Default version will never provide an effective solution for all in this term. Yes, "users play" as you say, but what it may give to a forum owner? There is no big profit from such a "game".
As about the developing your suggestion, it is quite easy. You should prepare few different bb_XXX_style.css files holding different CSS schemas for miniBB. Then alter users table with a
new field, which will store the value of XXX and would allow each member to change this from a dropdown under Profile (the similar solution is provided under the "Gender" code). This value should be read from bb_cookie.php, and if it differs from default, the script should substitute it for the $skin setting. That's all...
