The Comic Book Party Art of Ryan Dunlavey
Artist Ryan Dunlavey ("Comic Book Comics," "M.O.D.O.K.: Dark Reign") has posted a whole series of "just draw everything" commissions for Wizard magazine, most of which involve dozens of comics characters throwing parties and hanging out. There's a Green Lantern/Waldo mashup called "Where's Guy Gardner?", a "Limbo Lounge" full of departed comics characters, "Know Your Ninjas," an X-Wake for the death of Banshee, and a dance party full of 80s cartoon characters (below).
There's also an "Adult Swim Pool Party" illustration, where he comments that "about once a week some know-it-all 13 year old posts a comment on my Deviantart account about how dumb I was for not including or any other number of characters in this piece." WELCOME TO MY WORLD, DUNLAVEY.