Thanks for all the replies. I agree about it looking odd with the zombie popping up but no obvious hole or splinters, but by the time I read that post it was too late.
I added a few maggots, skulls and bones and here's the finished cake.
Unfortunately I only came 4th in the competition. I know it shouldn't matter but I spent ages on it and I thought it looked and tasted great. Guess I'm just a bad loser!