Some random typing-as-I-think:
Air
Civ-wide effect +1 movement to ships/flying creatures per node
Utility Ideas (Buffs, City Improvements)
"Fair Winds" - movement bonus for ships/flying units
"Fly" - as above, grant flying to units/tiles
"Wall of Wind" - city improv- archery units can't attack/ have penalty to attack
"Floating Tower" -city improv - +2/+3 line of sight?
"Flying Citadel" - lift the city off the ground (level 3 perhaps

"Harbour Winds" - sea trade route +%?
Combat Ideas & debuffs
"Downdraft" - ground flying units
"Gust" - Push back a targeted unit backwards one tile
"Wind Storm" - scatter flying and boat units 4-6 tiles away
"Lightning Bolt" - direct damage
"Chain Lightning" - tile attack
"Maelstrom" - AOE attack
Summon ideas
"Zephyr" - Non-combat scouting unit, great range, but permanent, not like hawk - 0(+1/air) str?
"Floating Disc" - slow moving unit with carry space
"Cloud giant" - moderate melee?
"Air Elemental" - high movement, flying combat
Earth Ideas
Civ-wide effect - increase chance of finding gems/metals works well I think
Utility ideas & buffs
"Wall of Stone" - city improvement ain't broke, don't fix it
"Dig In" - improved fortifications/ramparts
"Stoneskin" - as above, great idea for stack-wide
"Prospect" - cast on a mined tile, %-age chance of unearthing gems/metals
"Raise/Lower Land" - as above
Combat ideas & debuffs
"Tunnel Below" - destroy city walls/improvements
"EarthQuake" - as above
"World Crack" - create impassable terrain/tile?
"Pebbledash" - the AOE low level damage spell
"Scouring Sands" - like rust, removes metallic improvements
Summon ideas
"Earth Elemental" - has to be one of them
"Clay Elemental" - summon that can speed production or make a road, then expires?
"Sandstorm" - a unit with collateral damage to the whole stack, but small actual attack?
Fire Ideas
Civ-wide effect - Chance for tiles to change type, eg like global warming in vanilla?
Utility Ideas (buff and city improvement)
"Blaze" - as implemented (though I never use it)
"Flaming Arrows" - should be fire not enchantment imho.
"Wall of Fire" - city improv, does damage to enemies who cross it
"Elemental Lighthouse" - some sort of sea tile improvement?
Combat ideas
"Fire blast" - as above
"Fire ball" - as above
"Meteor Swarm" - as above
"Ring of Fire" -
Summon ideas
"Fire elemental" - obvious, but good