I'm trying to sort through a collection of DeepZoom sub-images based on arbitrary data associated with each image. The sub-images get loaded automagically through an XML file generated by DeepZoom Composer. I don't see a clear way to associate arbitrary data with a DeepZoom sub-image. 

The solutions that seem most obvious to me are brittle and don't scale well. Ideally, I'd like to put the relevant data in the generated XML file, but I'd lose that information on the next set of generated images. 

Is there a well-established way of accomplishing this goal?