I'd put it where you get the most presence - usually the arrival is when the little ones are looking all over the place, and leaving is when they tend to dart out to go to the next house in my case. I have everything angled and placed to their best advantage as the TOTs come up to my house.
It sounds as if your back garden is a good place for your decorations, since it also overlooks the main entrance, but it really depends on the foot traffic.
I LOVE the idea of a large skull clock... please tell me that the actual "hands" will be skeleton arms with a bony finger pointing out the number!
