There is a really strange one in St. Aidan's churchyard, Billinge, Lancashire. It is a flat coffin-shaped stone with a death's head surrounded by a snake biting its tail, and underneath there is a pair of bat wings!
Here it is: http://i300.photobucket.com/albums/nn2/Finbarpics/1%20Local%20History%20etc%202008/BillingeChurch4.jpg