I may have double posted, we shall see.
Anyways, so yeah I did a paint over to illustrate a bit of PKD’s point in regards to using refence and concepts. When I have an idea I usual do a quick 3D concept (usually in 3Ds max) then take the camera angle I like and bring it into photoshop and just grab pictures from the net and through them to create anything (textures, structures, points of interest, etc). You get a lot of happen accidents. Plus its a fun way to procrastinate from actually getting down to full modeling ;).
Good job so far with the additions! I hope you are seeing how each addition moves your art along the path to actually getting into the gallery.