Curtains.
It sounds dumb, but when a trailer sits around not being used, the sun can fade things, make them brittle, etc.
Lawn chairs and folding tables, so you can lounge around, outside of the camper.
Yes, covers for the tires also and a big sturdy awning that can cover the trailer a couple of feet above the roof, it will help with thge temp and elements. Make sure it drains away from living areas.