Hmm funny... I assume you refer to the attached hut right? I never noticed it before, I always thought its a large stone keeping the roof in place... but if you look closer it could be something like as skull as well.
So I cant answer your question, all mapping elements are taken from the Dundjinni forum, as I lack the possibility of creating nice objects myself. I assume I could do a few items in GIMP but actually I dont know what tool I should use to actually render objects myself. I am open to suggestions.
Right now I try to find some nice looking siege machnies, which is harder than I thought :/