Depicted are: Apu Nahasapeemapetilon, Bart Simpson, C. Montgomery Burns, Dr. Julius Hibbert, Edna Krabappel, Ned Flanders, Groundskeeper Willie, Homer Simpson, Itchy, Jimbo Jones, Krusty the Clown, Lisa Simpson, Marge Simpson, Nelson Muntz, Otto Mann, Principal Seymour Skinner, Major Joe Quimby, Ralph Wiggum, Scratchy, Troy McClure, Uter Zorker, Milhouse Van Houten, Waylon Smithers, Xena Warrior Princess, Yes Guy, Artie Ziff
By the way, I know there is another Simpsons Alphabet out there. I found it when I was over 3/4 done this one. Oh well, there's room out there for two of these.
Available as a T-shirt, poster and more at Society6.