I'm not posting it as any means of showing off, but rather giving an example. It's pretty well optimized on graphics, though could probably use a little more. And there are no tiled backgrounds because nothing really repeats:
That layout is around 95MB of VRAM. There's a ton of motion going on (the grass and many of the pine needles blow in the wind), and a lot of objects. But without sticking to power of two, that would end up being a nightmare to run. Your graphics look fantastic, don't get me wrong. And I do have layouts that go up to around 125MB, but optimizing will allow you to get a LOT more detail on-screen without taking a hit.
In your case, those large wall textures could easily be tiled backgrounds and then post an occasional crack or whatever as a sprite over top to make sure it doesn't get too monotonous. Then you could use a mask layer for your lighting (search it on the forums if you aren't familiar) and then post your windows/etc. as sprites over that tiled background. Your interior levels lend themselves well to doing this.