Use of old printing trays

I'd picked up old printing trays here and there over the years knowing I'd be able to make good use of them one day - I painted this one and filled it with lots of my treasures - there's beachglass, pottery, coral, seeds, marbles, lichen, pencil sea urchin spines, crab claws, sand dollars, bark, barnacles, seaweed, pebbles, mermaid's purses, shark's teeth, tiny dried roses - I can see it on the wall as I type!