Looks pretty good, even if you were in a rush. Still, it shows at some places, like the walls sticking out in the first chamber.
I did this for a web campaing im running called "The Demogorgon's Will" and is on the LvIII of a rival temple.
This one in particular was done in a rush, as the entire party was wiped out, and i needed to come out with an idea to dont lose them all, so they were captured and taken to the temple's torture room.
What I do for places that are supposed to be underground is the following:
1. Put the floor texture as background.
2. Draw the walls outlining the chambers.
3. Draw a box around the map as a whole near the Border.
4. Combine the Walls and the bordering box from Step 3 as a polygon with the MULTI POLY tool. This make a Solid object with a 'hole' where the chambers are supposed to be.
5. Apply glows, bevels etc.
The result of the steps above means you do not end up with an area like your map above. The map is GOOD, but with the Wall Shadows makes it appear as a structure that is standing above a flat plane as opposed to be something carved out of the surround dirt/rock.
I dont work much in this one, i just wanna have clear if this is what you mean, the thing is that i miss the walls, i would like to see it carved in the ground but with walls...