Here are some belly pics of my kids...Bailey likes sleeping on his back the most, followed by Claudia. It's hard to catch them with their bellies up when I have my camera handy, however!

Bailey:
As a baby, and then a couple more as an "adult":




Leo:




Leila:
(the first one is when we first got her - look how skinny she was, not that she's changed much - she's just more muscular now)




Claudia:
(I haven't had as much time to get pics of her belly, since she's newest, but she really sleeps on her back a lot!)