My problems are twofold:

Entire forest of trees are spawning, rotating and depth-sorting. But they're not moving. I tried a whole host of hacks and fixes but it's not quite the same as redesigning it again from the ground up.

Now that I've worked out objects and classes again, bringing the original shitty terrain hack into line will be nice and tidy. Rotation will break as well doing that, but the whole thing needs a good cleanup.

After the above is done I'm going to get it tiling mapsets (so I can reduce the size of the current terrain into manageable bits) and have it load them from the server as needed. Then it'll need a map format of some sort.

I think I'll keep most trees as randomly generated, but also allow for specific placement. This will save me time because I can just give it forest center, size and density.

After that we'll look at bounding maps and stuff. Trees shouldn't appear in rivers and players shouldn't be able to walk through crevasses. The easiest way will probably be to supply a 2-bit image for passable/unpassable and transform offscreen it with the terrain, then just get the pixel colour to test its state.

We can also do simple 3d models at some point. It'd be cute to do flat-shaded polygonal modelling. Polygons would be more flexible than scaled/rotated/skewed textures, but there are drawbacks to both.

Textures can have transparency, which will look great and help add a lot of detail to things.

Polygons are fast and can be a lot more complex.

Either way when all is said and done each object draws itself so there's no reason there can't be a mix of styles in the world, just not a mix per object.

This brings me to particle systems. Although 'thinking particles' are new to consumer-level modellers, they're pretty basic in programming. While you wouldn't want every tree spewing autumn leaves, having a tavern spawn drunks or a forest spawn birds isn't unreasonable.