Really cool idea! Some variations or inspirations from WoW could be interesting.
Like the more liquid-like Elementals. (Water Elemental)
Swamp Elemental, Mud Elemental, Beer Elemental/Alemental, Sand Elemental, Mercury/Quicksilver Elemental.
The more rocky/solid ones. (Earth Elemental)
Ice Elemental, Obsidian Elemental, Magma Elemental.
The windy-like ones. Gaseous if you will. (Air Elemental)
Wind Elemental, Dust Elemental, Sound Elemental, Snow Elemental
And the last category I can think of that can apply to multiple categories (Solid and liquid, liquid and gas, gas and solid)
Mana Elemental, Fel Elemental, Light Elemental, Shadow Elemental, Void Elemental, Nether Elemental, Drakkari/Mojo Elemental.
A lot of good ideas could be derived from WoW and the WC3 campaign.
Wowpedia Fandom
Wowhead