so Aqua can use ice, then making a char that from darkness his cold to create ice as well, would that mean that person can use water as well, or would he/ she be a pure ice user on a higher level (when comes to ice)

well I will start with just 1 (electric), make the second electric user some time later when the story has really started (aka, when they know who are stuff)
the ice will come last much much later

just for idea's, got a little list of other elements not used yet:
-magma (unless part of pyro)
-plant (often called nature)
-steel/ magnetic
-poison/ acid
-crystal/ noble metals (like silver)
-pure raw energy
-mind (not one I usually use in rp settings, but it is an official element in many believes)
-physics (pretty rare one to find, but some think the laws of physics, like gravity are also a type of elemental power)

you dont have to use any of them, just wanted to share these, most (aside the last one I think) could be useful some way or an other