Crafts? Sculpture? What to do with an inundation of slide trays?

My dear, departed Dad was a photo fiend. Specifically, the man took slides. Hundreds of slides. He and my stepmom would do slide show presentations of trips they’d taken for local retirement homes so I guess Dad kept multiple trays pre-loaded so they’d be ready for their shows.

And now I have them. Thirty, I think, slide trays. I have taken all the slides out and will review them at some point and see which I’ll want. I’ll keep a couple of trays for the existing slide projector. Maybe at some point I’ll get the slides scanned and transferred to disc. But whatever I do, I won’t ever load them up in these trays for storage. So now I have a stack of stupid slide trays taking up space.

I hate the thought of just tossing them out - I really try to keep my waste to a minimum and this is a largish chunk of waste. I did contact used photography equipment stores - nobody was interested. Ebay already has heaps of slide trays advertised and few bids.

So does anybody have any brilliant ideas for what I might do with these things? Does anybody know of a crafter or a craft that uses them? Someone who creates art from odd items perhaps? Any alternate uses for them that could render them good garage-sale material or craft material that a rec centre could use?