Suggestion for objects; pools. Magical pools, water fountains, etc. radiant colors as purple, green, blue, or just plain water. Maybe even dirty water. Good for caverns , castles, and alchemist lairs.
I know Fata Morgana enables some kind of pool construction, but ponds would be awesome, and small indoor lakes, too. Specially if can break the water level limit.
And... since we're there... can we have fishes swimming on it?
The artificial pools are great, but how about a few natural ones to drop in a dungeon? Something that the edges match the stone floor coloration. Something a water based creature can crawl out of.
Might as well be able to do pools of lava as part of this. I would think it would only be a simple texture change.
Don't forget ponds and manmade small lakes and the ability to personalize them, too.
Stone carved 'irrigation canal' so that I can build aqueducts