Any pose is fine. You can even do the thing with the bird. Be creative, and go wild. Even edit it slightly in PhotoShop if you want to try to do a little trick (just make it look like it would be possible in the game, even if not in a level with nothing else in it, like making a picture of your sprite bouncing off a spring (as small as possible, remember!). Nothing too extravagant, though, and preferably nothing larger than 1.5 times the normal size of your character at most.

~ Traft