Unfortunately that would definitely mean more space would be used and the icon wouldn't fit the vnode, let alone fit the (current) 1280 bytes reserved for icon storage.
Perhaps there could be some sort of glow effect derived from the icon itself when someone hovers the mouse pointer over it. I guess it would be a little difficult to implement, as some sort of hinting for colors and appropriate glow spots/paths would be needed. However, if done correctly the effect can be very impressive -- and not corny :)
Maybe animated icons. For example icons which reacts an events like mouse over, clicks... This can be used to visualize for what a app is good for when you move the mouse on it... At every point this must used very wisely otherwise you have a very chaotic desktop ;-). Technical it is more difficult and I thing not a point for R1.