I'm struggling a bit on this one. I've been trying to come up with a good metaphor for a "categories" icon that is effective at about 20x20 pixels. I had considered using the 'standard' sitemap icon (an example of which is here), but given that this is for a web project, I'd prefer to avoid causing any confusion for users who might be familiar with that icon and its significance. A filing cabinet metaphor would work, but distilling that down into a 20x20 pixel, single-color icon just isn't feasible.
Any thoughts?
Any thoughts?