A forest would be, indeed, good as hell! To fasten the process of creating one I\'ve searched for an old URL I found on the topic of
\"Image-Based Rendering of Vegetation in Real-Time\".
This method of rendering a tree is very simple. You have a model of an very detailed realistic tree with thousands of polygons on it. Now you make shots of this tree from different angles and you use this slices together with blending to simulate one single tree.

With that technique you can actually render a lot of good looking trees. You only have to change the first step. Instead of making one very detailed model of an tree you have to make x models. An example:
If you create two different models for each of four different tree-breeds you have already 8 completely different trees. If you mix em up, change their color a little bit and vary them in height (which is very easy because you only have to make the polygons bigger/smaller, not the slices) you have a forest that looks different from tree to tree.
Storage isn\'t that much of a problem I think, because the slices won\'t take that much space.
Edit: Very interesting link, if youre in
modelling plants .