I have a few idea's for new bending expansion that I hope are okay.

Eartbending:
Glassbending : Glass is made of sand after all.

Airbending:
Vacuum bending: Simply remove the air from a certain area and you make it impossible to breath, start fires and you can use it to cut.

Gassbending: The ability to bend gases other than oxygen like helium and natural gas

Waterbending:
Oilbending: Oil is a liquid and while this expansion isn't probably useful in combat, oilbending would make drilling for oil a lot easier.