I looks really good, I like the design of the city as well...

The biggest thing for me is the one-tone of the trees, it's fairly easy to see that they are just a layer on top of say, the map relief... since they are all the same shade (or at leat the tints are random and don't follow the hills etc)... Shading the tree layer (i think just a "multiply" layer with hand drawn shading?) could bring those tree's into line, and have them flow with the landscape...

Other then that, I'd suggest modifying the rooftops to be multiple shades as well, just slightly different random tints if possible, it's a bit washed with the same colour at the moment. The warehouses have a hard shadow on them too, leaving it like that would make it look like they're taller than the walls, which would probably not be correct... A lot of the shadows could use some changing really.. again I think modifying shadow height (might be a LOT of work, I dunno) for the buildings would give it that realistic look.. but definitely i think the castles shadow should be deeper, since castles are usually taller than their walls, at least their turrets are... as for city sights, I think a city that size would probably have a few plaza's, I'm going to say... 3? one major and 2 minor? it's a pretty big city so I think it would warrant such...

Your on track for a great map tho.. keep it up!