Fill in the blank...

OK then, for the next video I'll probably be sticking with the 'rotating' theme and making a bridge that swivels over a pit (perhaps it's operated by a nearby winch or lever):

HERE is an early prototype of the kind of thing that I mean (note that nothing is stuck down or cut to size in this quick example).

Anyway, if you look at the above image you'll see that the middle page contains a few textures that can be used to make the bottom of the pit as a separate room tile (i.e. it'll be a floor tile with a rotating vertical shaft at it's centre).

And if you look a little closer you can also see a little grey box (outlined in red) at the bottom. This is a roughly 2X3" space that could be filled with another texture - so does anyone have any ideas for what this could be? (note that it would ideally need to be something that ties in to this specific room/encounter - not something that's a bit random ;) ).