First of, welcome to the guild, and now to some quick comments before having breakfast with the kids.
All maps:
You should make some thinner lighter lines to separate the squares, the draw attention to them selves, which they of course shouldn't.
Map 1:
Coould need some more detailing - but looking good
Map 2:
The grate is rather big I think, and the green stuff to the east of the statue seems very thick flowing (but it might be of course)
Map 3:
Love the spiderwebs, the tile that broke of looks a little placed, normally if a tile breaks, it will still lay in its place but just have cracks and bit that has disspeared due to rain and wind.
Map 4:
All in all fine but the large rocks should cast longer shadows than the stepping stones. I suggest making a new layer and handpainting longer shadows with a soft brush (opacity 10-20) that will create the nicest shadows, but you can also place all those stone on a separate layer (or several depending on stone size would be better) and then change the drop shadow value for each layer.

Congrats on your first upload of maps and have some rep