Supposed to be 17, I can only get 16. Considering all the comic nerds here, I figure this should take no time. First off, let’s use spoilers so everyone can play. No cheating by looking at other answers until you put up your list. AFAIK, the correct answers are not listed by the artist.
Here are my 16
Spawn, Deadpool, Daredevil, Dr. Strange, Thor, Flash, Shazam, Thing, Green Lantern, Hellboy, Aquaman, Superman, Spider-Man, Punisher, Wonder Woman, Captain America, some X-man, I’ll go with Wolverine. My guess is I’m missing who wears the belt with pouches or whatever shoulders are between the cowl and the neck.