Yes, you can also do this in TG by creating (or using a pre-existing) single Image Map Shader, and then just referencing that one shader for any single objects or object parts that use it. So as an example let's say you have a huge single-object city model with 100 buildings, each of which uses a fairly generic "concrete" texture, but all are UV'd separately so you can retexture each model on its own if desired. You would probably have 100 references to a single texture. In many cases that would load into Terragen by default with 100 copies of the image! Which wastes a lot of memory. If you can spend the time to go through and re-reference each Part Shader's Default Shader to look at a single Image Map Shader for the color image info, that will save lots of memory. Granted that is a fairly extreme scenario I described, but I do know that some Poser models and other publicly available models do have some duplicate texture issues that can be solved in a similar way.
I should also say that this does point to something of a deficiency in how TG handles texture loading currently. In theory we should be able to detect duplicate references and only load one copy of the texture and handle that transparently instead of requiring all that rewiring of the node network by hand. But that would be something we'd have to implement in the future...
- Oshyan