It's on my list but I need to take care of a few more things first!
For the moment, you can control the grid snapping size in Settings > Display > World Tile Snap size.
The placements are currently based on the object's collision so they can't overlap and the player's position so some people have found precision decoration easier when at walking speed with no speed buffs.
If there's anything specific you're looking for in decoration let me know and I'll see what I can do :)