I guess I'm not looking specifically for an icon, just an idea of what I could use for imagery. I'm having issues today (probably that double cappuccino) imagining what kind of image i could use for something that demonstrates the capability to toggle the idea of "apply all [filters]" and "remove all [filters]". The image doesn't have to show both, just one or the other, and it would switch based on the state.
Of course if you have an icon (16x16), that would be great :) But really I'm just looking for ideas. My current icon set is basically the FamFamFam silk set.