How to Add a Filter to Native WordPress Gallery Thumbnails?

Hi,
I’m building a portfolio site and am trying to figure out a way to create a filtering system for all the content (thumbnails). Ideally I could continue using the native WordPress gallery (the tiled gallery) and then use a plugin or hack that would allow me to add some sort of keyword or tag to images. When a user is on the portfolio page it would initially show all the images but they would be able to click on a list of keywords to filter out every image that didn’t have that keyword/tag attached to it.

Alternatively, if someone knows of an existing plugin that allows for easy, automatic tiled gallery generation and filtering I’d be totally open to buying something that fit what I’m looking for. So far, I’ve only been able to find plugins that do filtered tiled galleries by having you upload each and every image to a separate post. Which is just too time consuming for what I’m trying to do with a couple hundred images.

Thoughts?