With the proposed "materia" system in place, I think it would be neat if they added slight aesthetic differences when inserting different types of materia, which would also help differentiate your appearance by giving two of the same types of gear a different look with different materia infused.

Ex. (thought not necessary, there are better ways to implement) armor/weapon with red/attack-type materia would give a feint red glow or something equivalent, whereas an armor/weapon with a blue/magic-type materia would cause a blue effect instead.

I do however agree that I don't want these to be huge flashy shows of sparkles. I prefer the subtle method of having auras/feint glows about certain points on the item, and generally have it more noticeable for darker scenes and less noticeable during lighter scenes (non-existant during sunlight would be a must).