I'm trying to design my own sprites and animating them in a proper or, at least, satisfying way is a hard task.
I post here some tutorials, maybe it could help. Some of them are related to inkscape, a very nice svg software.
http://www.spriteland.com/tutorials/animating-a-walk-cycle-in-inkscape-part-1.html
http://2dgameartforprogrammers.blogspot.de/2011/11/character-animation.html
http://www.angryanimator.com/word/2010/11/26/tutorial-2-walk-cycle/
http://en.wikipedia.org/wiki/Walk_cycle
http://www.devilsgarage.com/tutorials/2-frame-walk-cycle/
http://www.manningkrull.com/pixel-art/walking.php