Let's deal with this important question .
Oh and to recap (but imagesearch is probably better):
Baldurs Gate Icons come in three colors, offensive-red, defensive-blue and miscish-white.
Icewind Dale Icons similar but have a red tones for offensive, green for summoning... (with exceptions)
Planescape Torment with no real symbolic pattern.
Other..
Well mine is from Baldurs Gate.. why?
Since I think a icon with a gun firing doesn't tell me as much as an icon with a Bullet and and three halfcircles behind it (to indicate for example triple power).
The spellbook is kind of a toolbox and I like my spells to reflect that I use something technical like "Tyndal's Flurescend Warp Displacer" vs "Roar of Anger" (..or flatheads have a red grip, philips a black one).
I am in the dungeon of Shadowlords, and then half my screen is filled with the spellbook of rainbowcolors.
I'd like to think that I am not alone in that sentiment but the trend seems to be definitely away from "functional/runic/symbolic" icons to stylish.
So what would you like to see in Eternity?