You know I have to be more critical with your work than others right?
First off, beautiful map! For being a speed map, it is exceptional.
Now for the nit picks:
- I do not like the banding on the roofs at all.
- The roads appear to be convex. They should be flatter looking, especially if they are well used, and definitely "lower" looking than the land around them.
- Shadows are too uniform in their cast distance. I would suggest putting the objects on different layers and then using non-global lights to give them different shadow lengths.
- I think the tree tops are too flat looking.
- For the river, take a look at this map: http://maps.google.com/maps?hl=en&ie=UTF8&ll=38.817099,-120.933391&spn=0.012021,0.016823&t=k&z=16&om=1
That is a location in the foothills where there are some rapids. I like the coloration of the water as it changes in depth and speed. Also note the shoreline's vegetation. You'll have a lot more right next to the water unless it has been cleared.