Wii Picture Dumper

I'm interested making an app that dumps pictures on the wii message board to an SD card, but I'm not sure how I can get access to the pictures, or what format they would be in. I'm also curious if this has been done in some form already.

I dont believe this has been done before, I read a while back about someone trying to do it, and not succeeding (not trying to put you off trying btw), and they managed to find the text of message board messages. I'll see if I can find it again, probably wont be able to, but if I can it may be handy for you.