You could look online at RPG.Net, as the boards there seem to be going though a supers phase at the moment. As I recall, there have recently been threads about supers who get their powers from Elder gods and become eldritch, twisted, things of horror... Soviet supers... superpowered Dr. Manhattan or Superman types as conquerors... I think WWII supers... and even pulpy types like Doc Savage or the Shadow. There have also been some interesting discussions about what the world would be like, so if you've got the time and the inclination to do some worldbuilding that would work. However, none of the ideas were fully fleshed out, so all of those would require the aforementioned time and inclination. Of the previous ideas, I personally think the Mythos-origin and Soviet-origin supers threads were generally the best for me in terms of inspiration.
If you're not at all interested in doing the pre-campaign work or at the moment simply find it something you don't have time for, I don't believe you're in luck. A reasonably detailed "fan-made" pre-built setting is not something I've seen out there, which is a shame, because I think the Mythos and Soviet ideas, for example, have some interesting aspects to them that aren't generally covered by more mainstream supers settings, and have sufficient depth and breadth to have what I suspect would be a non-trivial design headspace. However, I think they failed for several reasons which lead me to suspect most fan-made projects will fail similarly. In the event you DO find one, please post it here, as I'd be interested in it.