Right side of the poster
From right to left, front row to back row.
Spider-Man from The Spectacular Spider-Man (2008 animated TV series; Earth-26496)
- Confirmed by Christopher Miller, one of the writers and producers of Spider-Man: Across the Spider-Verse
Pavitr Prabhakar / Spider-Man (2004 Spider-Man: India #1; Earth-50101)
This look and costume were shown in a YouTube video by Sony Pictures Entertainment
"Werewolf Spider-Man" (2007 Marvel Zombies/Army of Darkness Vol. 1 #5; Earth-7085)
"Last Stand" Spider-Man (2003 Amazing Spider-Man Vol. 2 #58; Earth-312500)
Gwen Stacy / Spider-Woman (returning from Into the Spider-Verse (2018); 2014 Edge of Spider-Verse Vol. 1 #2; Earth-65)
Tarantula (2006 Ultimate Spider-Man Clone Saga; Ultimate Marvel universe / Earth-1610)
Maybelle Reilly / Lady Spider (2014 Spider-Verse Vol. 1 #1; Earth-803)
Spider-Man from Spider-Man: Unlimited (1999 animated TV series; Earth-751263)
Peter B. Parker / Spider-Man (returning from Into the Spider-Verse (2018))
In the trailer for Across the Spider-Verse, he was also wearing a pink bathrobe like in the poster:
Spidercide (1995 Amazing Spider-Man Vol. 1 #399; part of the 1994 Clone Saga storyline; Earth-616)
Hobie Brown / Spider-Punk (2014 Amazing Spider-Man Vol. 3 #10; Earth-138)
Margo / Spider-Byte (2018 Vault of Spiders Vol. 1 #1; Earth-22191)
Eugene "Flash" Thompson / Captain Spider (1977 What If? Vol. 1 #7; Earth-78127)
Spider-Man wearing Spider-Armor MK I (1993 Web of Spider-Man Vol. 1 #100; Earth-616)
Cyborg Spider-Woman (to be introduced in the film)
Source: Official action figure merchandise for the film
Spider-Man wearing Spider-Armor MK II (2011 Amazing Spider-Man Vol 1 #656; Earth-616)
Charlotte Webber / Sun-Spider (2019 Spider-Verse Vol. 3 #3; Earth-20023)
Left side of the poster
Miguel O'Hara / Spider-Man 2099 (1992 Spider-Man 2099 Vol. 1 #1; Earth-928)
Mary Jane Watson-Parker / Spinneret (2015 Amazing Spider-Man: Renew Your Vows Vol. 1 #1; Earth-18119)
Spider-Man from Marvel's Spider-Man (2018 video game developed by Insomniac Games; Earth-1048)
Ben Reilly / Scarlet Spider (1994 Spider-Man Vol. 1 #52; part of the 1994 Clone Saga storyline; Earth-616)
Sir Peter Parker / Prince of Arachne (2007 Spider-Man: Fairy Tales Vol. 1 #4; Earth-71004)
Jessica Drew / Spider-Woman (1976 Marvel Spotlight Vol. 1 #32; Earth-616)
This look and costume were shown in a YouTube video by Sony Pictures Entertainment
Doppelganger (1992 Infinity War #1; Earth-616)
"Ends of the Earth" Spider-Man, wearing Spider-Armor MK III (2012 Amazing Spider-Man Vol. 1 #682 "Ends of the Earth" storyline; Earth-616)
"Bombastic Bag-Man" / Spider-Man wearing a paper bag as a mask (1984 Amazing Spider-Man Vol. 1 #258; Earth-616)
Julia Carpenter / Spider-Woman (1984 Marvel Super Heroes Secret Wars Vol 1 #6; Earth-616)
Patrick O'Hara / Web-Slinger (2014 Amazing Spider-Man Vol. 3 #9; Earth-31913)
Spider-Cat (2011 Spider-Island: I Love New York City Vol. 1 #1; Earth-999)