Sweet, Dailyman, keep it coming! I just took a longer look and I'm a bit puzzled about the fourth character. I see Iji, the Golden Knight, the blue Knight from Castlecrashers, but who's the other girl? She looks a bit like Chun-Li from Streetfighters.
Also I wonder what made you pick those specific characters? Are they of your favorite games, or was it more of a random selection? Hopefully the blue Knight will actually get in the game eventually.
Oh, and don't forget to be consistent with the thicker outlines (see the inner parts of the legs from the two girls and GKs right arm)!
On another note:
I had a weird error when I started IB today:
action number 4
of Create Event
for object Control:
Error defining an external function.
I unplugged my gamepad, started the game again and it worked fine. Maybe this was because last time I played I set the controls of player 1 to gamepad. I have a Logitech precision which is known to make troubles with GM (can't configure the buttons for Spelunky other than in the config.ini for example). No idea if this can be fixed, just thought I'd let you know.