To get new users you need content, no matter what type of content it is you need it to attract people. The amount of people you will attract it will be decided on the type of content.
The main problem is that you cannot provide a satisfying motivation to unique content providers. back in the days people shared more easily A They had knowledge and made effort on it. B they was younger.
Noways the youngsters won't share because they can't find a reason to do. I believe back in the days the motivation was the recognition but thats no more.
Even if you focus on tournaments GFX or League it won't get much activity unless pool prizes, and if you only attract people with pool prizes they will just come for them and then leave they won't stay
EDIT:
A Cool idea for a mini-tournament & learning programming is Code this week.
You set a theme and people try to code it, the judges pick up the codes and rank them also they provide comments on improving.
But whos gonna take this position, is there any guy who is willing to get this much trouble for nothing? I bet there is. Is he skilled enghout to keep it up? i doubt it