I'll keep poking around. I found the article that I was looking for about the wooden idols and I don't see an awful lot of similarity there (to the Sheelas), although the sample is tiny.
There are the frog/female symbols from Catal Huyuk onwards and also lots of birthing figures but they are not really the same as the sheelas which are more about display .
I just checked through a book at home to see if I could find a picture of the frog/woman and noticed a tantalising photo of the fish goddess of Lepinski Vir. What a way to pass the time, eh.
Anyway I just did a search to see if I could get hold of an image online and I see that someone has already made the link (pun intended ;)):