OK ProBpony, I hope you don't mind, sort of hijacking your image thread, but actually it's the answer to your question.
As Ulco mentioned, there is the possibility to assign a shader directly in your object's shader network. If you run it through a Transform Input shader with "World Space" checked, you'll get an exact "projection" of your shader on your population. The advantage of this method is, you can do this for each part shader separately. the downside is, that it might look a bit too sharp, if you're using an image map shader for example (see image right). But depending on which objects you're populating, it might be the desired effect.
This method doesn't work without the Transform Input shader: each instance will have the identical shading.
If you're using the "Tint diffuse Colour" method under the colour tab of the population, each single instance will have more or less an idividual colour tinting depending on the shader you use.Looking like sort of a mosaic so to speak (image left).
For a sharp projection you could here as well put a Transform Input shader with World Space selected in between. This method affects the whole instance.
So, it's up to you to try, which method works best for you.
