I like this new forest tileset better than the old one! I say keep experimenting and making some more grass/dirt tile sets and post them for advice.
There's a lot of stuff to comment on here. I'm sure someone else can give you better advice but here are my thoughts. I'd recommend you push the detail on some of these pieces further. For example, the warehouse, you can create more detail chimney stacks, create a small door on either side for people, maybe make a big sign over the warehouse saying something like "Ferris Air" or whatever you want.
I'm not entirely sure what the image is between the last tree and the large building. Is it a shack or a shed? I like how it's in perspective though. Maybe you can do that to the building too.