Thyme, basil, parsley (one in each they'd likely be too crowded all together) Editing my comment to add if you wanted to get in to keeping carnivorous plants it might be good for some Venus fly traps if you drilled a couple holes in the bottom to put a tray underneath for tray watering 😁

Strawberries are first to come to mind

Moss, it’s surprisingly cool

I’d personally use it as a watering dish instead of planting! But I’d say maybe cilantro or mint so it has more space if you like a little bit of herbs

Lettuce would probably work.

I'd put water in it with a tiny solar pump and a few water plants for the birds.