Rutra is exactly right in what he says. Also about GeoControl. I don't know if you want to do too many new things at once, but it is a terrific product. I have used GeoControl1 and GeoControl2 since the beginning. Cajomi has a great discussion on how to bring it into Vue as a procedural terrain. It does make the terrains very life-like. As far as I'm concerned, it's a must to have along side of Vue. While I do use one terrain often, I do use multiple ones, especially if I want to bring in rivers. It's so much easier to work with more when you are working with water.

While you can create your own trees, either through creating new leave groups with the veg plants or building new models, I suggest that learning Vue is enough. There are great trees at Cornucopia 3D. I'm not sure if I saw any Aspens. I have been using Aspen from the xfrog Billboards when I need them. But I did get a notice from Linda of Incredibly Lush Plants (Cornucopia 3D) that she will be coming out shortly with a series that will contain trees from the western region. There might be others out there.