I just thought I might recommend The Atlas of Foreshortening by John Cody... not only is it an excellent reference for numerous anatomy questions, it is filled to the brim with pose after unusual pose, and I think it would be a boon for you when trying to draw poses like the one you chose for Spidey. A teacher recommended it to me recently, and I'm eternally grateful.
I agree with the earlier posts about proportion of characters, but I'd also like to congratulate you on imbuing all of your figures with excellent character of spirit. I can definitely feel what kinds of guys these are.
Also, your interpretation of the Thing is so quirky and cool... I love it.