Among others, we have kitteh versions of Spider-Man, Wolverine, Galactus, Storm, Dormammu, Dr. Doom, Iron Man, Captain America, Thor, Phoenix, Magneto, and the Hulk.
Edit: I now see that "Captain caturday" (this isn't you is it, Jerry Coyne?) has explicated the full pic as follows:
For those that are curious, here they are, from top to bottom, starting from the left
Column 1: Spidercat, X-elebenty3, Taskmeowster, Dormameow, Shumeow-Gorrah, Meownix, Deadpoolcat the merc with the meow
Column 2: Catverine, Stormz aka Ororo Meowroe, Doctor Tinydoom, Senticat, Supurr Skrull, Meowneto
Column 3: M.O.C.A.T., Ironcat, Captain Ameowrica, Moar god of thunder, Haik, She-haik
Column 4: Catlactus nommer of worlds, Ameowterasu, Purron Bonne, Mewtiful Joe
Column 5: Akumeow, Chris Rawrfield, Rawryu, Catte son of Purrda, Cat Viper, Purro meowverick hunter
Column 6: Spencer the bionic catmando, Cat-li, Rawrthur, Hsien-meow
Column 7: Mayor Mike Rawrgar, Felicia who has been hit my Anakris’ mummy curse, Albert Whisker, Purrish, Jill Catlentine, Meowriggan.