To measure iconic value i follow the "cosplay rule". If you see someone cosplaying as the character in a comic con, would they be instantly recognizable?, would they be confused with other characters?
about design:
In the spiderman movie with the green goblin, something that stood out about the design is that when he took of the mask you can still see the green goblin`s essence on the face of the actor.
Your characters have an unique and recognizable design because they are anthropomorfic animals, so i recommend you to go for something that fits the species they are.
Also, you gotta consider how your character`s powers work when making the armor.
Ex: A heavy armor may hinder a speedster`s movement, but could be useful for a strong user who can carry that weight without trouble.
While i like the knight style you are aiming for with Flare, i think it would look cooler if you manage to mix the dragon elements with the knight theme. Maybe some cape that can turn into wings and to make the helmet shaped like a dragon`s head?, not sure exactly what, but see what works for you.
I love the ice tiger helmet. It looks cool and seems to fit perfectly for an ice user who may need to maneuver on icy surfaces (like skying) and the visor protects the eyes which is something vital in the snow because of strong winds and the snow`s reflection with the sun.
Selena in her regular outfit is already iconic enough, so i would recommend to use some of these aspects in her aquatic armor.
If i remember well from your older posts Selena can grow when in contact with water, so something flexible enough to not break with her size change and that leaves enough space for that contact with water may be useful. Maybe she can carry some water tanks for that (how much would depends of how much she can carry without trouble). And the most obvious thing, to be able to swim with it. I think a cloak would make it harder for her.