Don't over-pack on clothes, but do have warm jackets and poncho rain gear. Be sure to have enough prescription meds and over the counter stuff that you use. Take chargers for cameras, cell phones, etc. Have a comprehensive tool kit with hand tools, electrical tape, duct tape, iron baling wire, wood and machine screws, crazy glue, and jewelers screw drivers, fuses and light bulbs, butane log lighter and a cheap digital multi-meter. Have emergency road service info handy and maybe some road flares. Take a good first aid kit. Some fun board games too!
PS: Avoid putting "stuff" in bags and cartons in the aisle, shower, dinette area, etc. Clutter and trying to find things can get on your nerves. As small collapsible charcoal grill, briquettes and starter fluid is nice. A grill pan can be put on a camp fire place to cook eggs and bacon, hash browns, etc. Outdoor cooking really has its charm.