My sunflowers produced enormous leaves this year (not to mention 12-foot tall plants) so I used one of the leaves as the pattern for a sand cast concrete birdbath for our garden. It's about 18 inches long by 12 inches wide with nice wide edges for the birds to perch upon.
The casting wasn't really hard at all. I'm waiting for the concrete to finish curing (in about another month) then I'll add sealer to protect the surface and make it easier to keep clean.
If you want to make one of your own, you can find step by step how-to directions for making a sand-cast lightweight concrete bird bath plus lots more ideas for unique garden craft projects at Squidoo.