Well crikey... who the hell is left that I haven't guessed? Elite? Certainly doesn't seem like something Lucas would send.
Winner winner chicken dinner, same to you Nekov.
A. Puppies (water theme)
1. Hotel of the Laughing Tree - In a River in the Woods
2. Moving Mountains - 8105
3. Grails - Deep Snow
B. Chad.boi (water theme)
1. Frameshift - La Mer
2. Mob Rules - Dykemaster's Tale
3. Freedom Call - Ocean
C. Evermind (water theme)
1. The Gentle Storm - Endless Sea (Gentle Version)
2. The Gentle Storm - The Moment (Gentle Version)
3. The Gentle Storm - New Horizons (Storm Version)
D. kingshmegland (water theme)
1. Gaillion - Letters From The Skipper
2. Jars of Clay - Flood
3. RPWL - The Fisherman
E. wolfking (fire theme)
1. Virgin Steele - The Burning of Rome
2. Virgin Steele - Through Blood and Fire
3. Black Majesty - Firestorm
F. TAC (water theme)
1. Storyteller - Curse of the Seven Seas
2. Lords of the Trident - Brothers of Cain
3. Heart of Cygnus - Lost at Sea
G. Sacul (fire theme)
1. Kyuss - Gardenia
2. The Stooges - Down on the Street
3. Alter Bridge - Blackbird
H. Nekov (2017 theme)
1. Úlfur Eldjárn - Kosovo
2. Enemies - For Karla
3. Enemies - Play Fire
I. Elite (2000s theme)
1. Adagio - Fire Forever
2. Across the Delta - The Loop
3. Green Carnation - Pile of Doubt
J. Stadler (70s theme)
1. The Grateful Dead - Terrapin Station
2. Jethro Tull - Dun Ringill
3. The Rolling Stones - Moonlight Mile
K. Indiscipline
1. Johnny Cunningham - Star Lullaby
2. C_ingon - Malagueña Salerosa
3. Norbert Leo Butz - Moving Too Fast
L. Parama the Owl-Roamer
1. Sacrificed Alliance - Verdancy
2. Ne Obliviscaris - Forget Not
3. Wilderun - The Means To Preserve
Guessed letters: L SCRIPTED AGONY