New Avengers #53

Who are the possible new Sorcerer Supremes contacted by the Eye of Agamotto? comicbookdb has a more complete cast of characters for this issue than Marvel Wiki (which doesn't have any extras), and I can make a good stab at correlating them with the comic panel, roughly in rows from top to bottom:-
Brother Voodoo, Jennifer Kale, Topaz, Satana, Tigra, Dr Doom;
Morgan Le Fay, Dr Druid, Hellstorm, Derwyddon, Baron Mordo;
Scarlet Scarab II, Cyrus Black, Modred, Soulfire;
Wong, Hood, Talisman, Mr Rasputin, Selene, Hellfire;
Wiccan, Devil-Slayer, Ghost Rider (Johnny Blaze), Scarlet Witch;
Magik, Spiral.
There are differences from comicboodb's list. I've used Dr Druid rather than Druid (of the Secret Warriors) - Dr Druid may be currently dead but it looks like him and Druid isn't magical. I've used Hellfire (from #51's cover) instead of Kaluu.
There are some other questionable attributions. Eg both comicbookdb and the Marvel Wiki claim that Mr Rasputin is here but the only other completely bald guy apart from Wong is the small pic in the middle with alien-looking big white eyes. But since a similar pic is included next issue and comicbookdb nominates Rasputin again I'll go with it.

There are some obscure characters here:-
Mr Rasputin fought DrS in ST#145 and only reappeared in the Mutant Misadventures of Cloak & Dagger #1.
Cyrus Black fought DrS in Defenders #6, DrS(1974)#34 and tangled with Nighthawk in a backup tale in Tales to Astonish (1979) #13.
Talisman is the Aboriginal Australian who was introduced in the 1st Contest of Champions but subsequently only showed up in Quasar #23-25.
Scarlet Scarab II fought Thor over the Eye of Horus in Th#326.
Derwyddon is an ancient Druid who helped Gargoyle in the latter's mini-series.
Soulfire fought/helped Daimon Hellstrom in Hellstorm: Prince of Lies #4-5.

We've already seen Hellfire, Hellstorm and Wiccan in the last 2 issues.

Of the others:-

In Brother Voodoo's last appearance in this title (#29-30) he was helping the post-Civil War Registration forces against his friend DrS and the NAv. But he may well have been the Skrull replacement uncovered in Black Panther (2005) #38. His real post Secret Invasion apps have been (Cable &) Deadpool #47-48, Hulk (2008) #9 where he cured Hulk of being a Wendigo, and Ghost Rider (2006) #32 the conclusion of a battle between multiple other GR's and GR Danny Ketch.

GR Johnny Blaze has just come from that story arc in GR(2006)#26-32.

Tigra's been a feature of the Initiative series for a while, taking time off for War Machine (2009) #8-10 before quitting to form the Avengers Resistance in Av:I#25.

Ex-Defender Devil-Slayer is here after being on the Hawaii Initiative team in Av:I#14,17-18.

Jennifer Kale has done quite a bit since her days with Man-Thing. Fairly recently she starred with Satana and Topaz in the Witches mini. Then she was in the Florida Initiative team during SI in Av:I#19, but the team broke up during Marvel Zombies 3. And in Marvel Zombies 4 she was part of the new Midnight Suns which included Hellstorm and Werewolf (By Night).

Topaz started off in Werewolf By Night but has become a frequent DrS character, lastly in DrS: Flight of Bones limited series. Then Witches.

Satana was resurrected by DrS to take a heroine role in Witches. In Nick Fury's Howling Commandos #6 she played the heroine again (with Brother Voodoo) against her brother Daimon Hellstrom. But in Legion Of Monsters: Satana she took revenge after being forced to be a 'heroine'. And in Hood's Dark Reign series she provided him with info about Dormammu.

Modred the Mystic is another character who swings between good and evil. Lately it was evil as he returned Chthon to Earth in Mighty Av #21-23.

Morgan Le Fay was most recently seen falling out with Dr Doom in Dark Av #1-4. Unfortunately that means she's currently trapped in prehistory.

Dr Doom has recently welcomed the Asgardians to Latveria in Thor #600-601 as part of a plot hatched with Loki in DR: Cabal. Then he attended Cabal meetings in DR: Hood #2 and MAv#24.

Scarlet Witch has been keeping a low profile since House of M. That definitely wasn't her in MAv#21-24, it was Loki in disguise.

Dr Druid was Ancient One's trainee before Stephen Strange. He's had a varied career including Monster Hunter and Avenger.

Baron Mordo is a longtime foe of DrS last seen in the Offenders team fighting the original Defenders (including a past version of DrS) in Hulk (2008) #10-12.

Wong is of course DrS's longtime manservant who is usually by his side - lately in our Annual #2 and Friendly Neighbourhood SM #24.

Selene is mainly an X-villain (although she did pop up in Witches #1). This issue is placed within the X-Men's Necrosha event in which she has the pivotal role. Before this app there was X-Necrosha: The Gathering and X-Force (2008) #11 where she picked some accomplices including a resurrected Caliban who would enable her to bring back other dead X-chars in the main event that will follow.

X-woman Magik is currently the soulless Darkchylde but she was brought back from Limbo in the X-Infernus mini-series.

X-villain Spiral was latterly in Red Queen's Sisterhood of Mutants in Uncanny X-Men #508-511.

Many of the potential Sorcerer Supremes will show up again next issue but others will leave the game here:-
Scarlet Scarab, Soulfire and Talisman leave more permantly because they haven't been seen again.
Jennifer Kale, Modred and Spiral will be part of Nightmare's army against Dr's Voodoo and Doom in DrV: Avenger of the Supernatural #5.
Satana will next share the spotlight of Deadpool Team-Up #892.
Morgan Le Fay will be rescued from the prehistoric past by her daughter Caroline in Fearless Defenders #12.
Hellfire returns to the Secret Warriors in DAv#9 and then back to their own series from #7.
The real Scarlet Witch will remain among the missing until the Av: Children's Crusade limited series. And Loki will continue to impersonate her for a few more issues of MAv.