Any ideas for the covers of florescent recessed lighting?

Maybe you can decorate them (modpodge or mosaic) and turn them into planters!

Oh, that's a thought. I could paint them or something - use them as an art base. The "lenses" are quiet large; so not sure about the planter. They are the long rectangular ones that go in drop ceilings in offices. I am repuposing the light fixture part as grow lights; but don't want to throw away the cover or "lens".

Could you attach hinges on the long side (Gorilla glue?) and use as doors on a simple set of shelves? Perhaps on a potting shed cabinet to hide the messy things from being full-on displayed. To strengthen them as doors and adapt to the size you need, build a wooden frame and insert the panels in each frame. Cover the edge where the panel meets the frame with screen door molding. To keep the panels from falling out the back of the frame, use metal flat bar run diagonally at each corner of the inside of each door. You could Modge Podge colored tissue paper to the inside of the fiberglass to diffuse the doors even more if they are too transparent.

If you want to use them outdoors, how about using them in a semi-private fencing, much as you would with lattice panels? It could be quite cute on a deck or patio to shield functional necessities from view. (Everyone has something they'd rather not see from their favorite seats).