Alright, going back to the subject of adding objects to existing styles - I'm going to do the LPII ones very soon, but the official styles may be a bit further away.
As long as you weren't planning on needing to use the new objects, you can still go ahead and create levels of course - the new objects will be added at the end of the style, so they won't cause compatibility issues with existing levels.
I won't necesserially use all the available slots - it depends what objects make sense for the style too, and I'm only adding *new* object types, not more objects of existing types. For example, I'm not going to add teleporters to the Tree style, but probably will add them to the Psychedelic style.
Most additions will be re-using graphics from the LPIII sets (possibly recolored).
Additions.
Tree: Updraft (Sky)
Purple: Teleporter (Martian), Slow Freeze (edited version of Lab radiation object)
Psychedelic: Teleporter (Circuit), Radiation (Lab), new object (original)
Metal: Locked Exit (original), Button (Circuit), new object (original)
Desert: Updraft (Sky), Radiation (Sky)