I also recommend including a one-paragraph phony story to go along with the photo, fabricating how you happened to capture the photo. This is not required, but adds to the fun
There's phoney stories aplenty on his website. All about magic skills and ghosts and boggarts and things that go "Wooooo!" in the night. Though looking at last year's winners, the competition seems to be pretty stiff, and Mr Grzelka's "let's run a clone brush over this one!" and "Oooh! Look at the dust on the lens!" and "Look! A reflection from a whiteboard!" efforts probably wouldn't even warrant a "Thanks for submitting" note.