I see. How would I go about making a graphics file for this tilemap, then? What I did was create a savestate in level 103, which uses the rocky hills background, open it up in RacingStripe, moved some things around, and saved it as a .stim file with the address A800. Then I converted it to a .bin file and inserted it.
This is what my bypass window looks like. (100 is the tilemap file I created.)