I quite like them, sand is a bit bright yes.
I recommend taking the wall tiles, the lowest brick areas, and add more definition - they look photoshoped rubberstampy. Just a bit blurred, more like a
Also, try erasing the sand at the base of the walls, and drop some actual sand tiles on a lower layer and apply it over.
(if if you are using a non-layer gfx editor, that can handle transparency, make a gfx same size as wall tiles but all sand, rub out the sand that is in the wall tile areas at the base, then copy/paste over sand tile img, to get smooth sand up to base of wall effect)
These are just suggestions, and not to imply you don't know these tricks, I just went into detail because that method makes it pretty easy in case you weren't aware of it.
Good work, I can't wait to be fighting monsters in there.
