I recently the sprite site we typically use has been replace has been replaced with a VIST IMGBOOT.COM so as an alternative use http://www.pokestadium.com/pokemon/sprites/
Thought I would answer this. If you want a solid image hosting site, use http://imgur.com - they have no bandwidth limits or anything.
However unless you're using animated sprites you can use our sprite section here: http://pokemondb.net/sprites Just go onto a Pokemon, right click and click "Copy image address" then use that in a picture.