Camera angles are so-so, they're a bit low. If you show the end of the world, make it ocean ONLY - horizon can be explained (or add waterfalls at the end and say it's the 15th century). Also, keep the height the same the entire time.
People pointed out there's no fog because, practically, there is none. Unless the black is intense, which is, most of the time, indoors, it doesn't count simply because it just shades things dark. I'd recommend a white, light blue, dark blue or dark teal, play around with them.
Don't use blizzard trees and this angle. It just looks... bad. They're made to be viewed from above, so that the overlapping leave mash can't be seen in two layers. Try putting shrubs on world trees, using giant bushes or putting shrubs in trees.
Like Ghenjis said, use lordaeron rain, also: camp fire / torches + rain? Put a centaur tent as cover. Units aren't too good looking, they stand out too much, if you tint them darker and/or make them black team colour, it usually fixes that up a bit. And if you're using buildings - make sure to remove the ground texture or make a doodad for the facing. It looks way better.
Now, as far as I've recorded, cacti don't grow on beaches, and rock types don't change dramatically either - you switched the tileset doodads to Barrens, I can see that. The Naga and Night Elf are huge amounts of clutter - keep it lower, ie. size down Z scale, or put in variation, ie. flowers. And you may want to make the island a bit bigger.
Two side notes: Ninja terrains. And so does other guy, forgot his name.