Your best bet is Heroclix. They are cheap plastic miniatures that are easy to mod or paint over. My next suggestion would be modeling dollies. Reaper and Hasslefree sell these.
There are only a few couple of Super Hero miniature ranges out there. Not many in a variety in a body type suit. Heroclix, Pulp City, SuperFigs, Crossover, and soon Kitbash games are about it. Maybe one or two others I'm forgetting. I wouldn't use Knights Models Batman or DC Universe for this project. To expensive and fragile. Same with the upcoming Marvel Crisis Protocol. To expensive for modding.