Charlaquin
Goblin Queen (She/Her/Hers)
You could go with Paracelsus‘ tria prima: salt, sulphur, and mercury.
I am bored of the four elements but I have all the inspiration of a brick and do not want to make the elemental planes of the periodic table regardless of how entertaining it would be.
does anyone know any other options that could add on to water, rock, air and fire that would be great both from old myths and more modern tales?
Rot Lop Fan is here and would like a word.You could go with the Green Lantern corps color spectrum and associated attributes.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.