It's pretty much like now. G's scene is actually built out of stuff that tiles (aside from their grass, which was a rough sketch). So that means there are the following layers:
1. Sky layers (several, actually)
2. Background parallax layers (2 -- in this case, the distant buildings you refer to).
3. Actual interactive objects that you walk past (buildings, trees, and so forth -- the two buildings in the foreground are this).
4. The actual main index of characters and monsters and crates and walls/grounds and spells that you would normally collide with, plus their attendant doodads and details.
5. Any sort of foreground stuff that your characters/spells walk behind. Usually there's not much of this.