Nice one, very creative here some tips/hints
- Like Temuzu said, mix up the textures, make it look a bit more realistic!
- Improve the hills behind Isengard a bit, level it up a little bit, and don't make it like you could just walk on it. Also, some point are pointing out like they are some kind of towers. Either increase the surrounding hills, or level it down. You also could easily use some change between textures in here. Try to make it look (also) realistic, like reall hills would look like.
Btw: I saw you did this on some "lower" hills, try to use it on the bigger ones as well.
Here an example how it could look like, note# this is from another game, but it can easily be done.
- Remove as much props/villages/camps as you can, it will lag with such a detailed map for the players. (Just I quick gues) seeing it's Siege mode. Most of these spots aren't really going to add anything to the siege it self. Taking the size of the map with it.
- Make the roads way smaller, then what they are right now. And try to use the weight, and hardness to make it a more "softer" road. Instead of these big straight roads.
In overall, currently it looks more to a conquest-mode map then a siege map.
Anyway! I hope you can do something with these hints, keep it up! Looks great so far.