Currently, the level theme (main tileset) and the working tileset are completely independent of each other. This makes sense when you're just grabbing a piece from another set, but it's a little inconvenient whenever you're starting a new level (because you have to choose your tileset twice).
I suggest making it as follows:
- If the level is blank: Change both
- If the level contains objects and/or terrain: Keep current behavior.
Excellent idea. Is implemented in the next version.