Using the new resources I have, I've rebuilt the level generator, generating diorama levels with a wooden border again. I was pleasantly surprised how well the level generation code looked and worked, after not looking at this code for a year. Here are a few screenshots showing the progress. At this point I only have 5 variations of tiles, so there is a lot of repetition, but it's easy to add more tiles. Here are some screenshots:
Next is path-finding!