In fact, we are taking delivery on this beauty tomorrow morning!

Here's a search to start with:
http://www.houzz.com/photos/bath/%22custom-tub%22-
and
http://www.houzz.com/%22unusual-tub%22

You could use a 'regular' tub and do special things with it :)

Here's one we designed / made recently in Seattle. You can see it on our houzz page, or read about it in this article recently published - http://seattle.curbed.com/archives/2014/03/nk-woodworking-wood-tub-architectural-art-carved.php