A second character, hmm, well there is a small boat-load of characters I probably would have been interested in trying.  I know I considered She-Hulk and Zatanna for a bit before zeroing completely in on Ms. Marvel.  Supergirl, Batgirl, Starfire, while not a thing in this roleplay did have some ideas for 'good' villain characters, like maybe a Caitlin Snow/Killer Frost who did not descend down the crime route.  There are a lot of ideas out there, those are just some of the surface scratchers.

As for characters from other sources...well not really too knowledgeable about other publishers and such.  Maybe TMNT, Voltron, Harvey Birdman[just kidding about that one, honest], Cybersix, Gargoyles, really depends on what exactly would be considered other publishers and all that.