How do I make a texture image a group of faces or a model feature
2 Answers

That is a good looking model. What was it made in?
Regarding the textures, I don't believe there is a way to transfer those into the actual stl/obj part.
I'm not an expert on textures, but my understanding is that they simply live "on' the model (like a decal), and are used by the graphics/rendering engine to give the illusion of detail, but still keep the triangle count low.
A program like Mudbox, or Zbrush can be used to "sculpt" additional detail into the base mesh, but I'm not sure if there is a way to easily "stamp" it in from your texture map.
I'm interested to see if anyone has some better options though, it looks like an interesting project.