Nice work, the walls stand out now and are clearly walls. The sand pit in the centre might do with some more texture or maybe even just a noise filter. And then of course you'll want some of that sand to be spilling out on the stones around it. I really like maps that have a bit of mess and debris scattered around, it helps to make the place look like it has felt the passage of time.

I like the details you have so far, but the rest will depend on what it is going to be used for. The windows are great, clearly show their position without getting in the way.

cheers,
Meshon