I'm a fan of Maxxis m8008 ST tires. You'll get a lot of input and lively discussion of ST vs. LT tires (both for and against).
You may want to consider vent covers so that you can have them open in inclement weather.
Since it has a slide out, you may want to consider a slide topper to keep debris off of the top of your slide.
You may also want to get a good triangulation stabilizer system. I've just installed the SteadyFast system on my camper, but haven't gotten to try it out yet.
And then there's always good between the wheel chocks, Andersen Camper Leveler, a good water pressure regulator (Watts), etc. There's always some kind of goodie to pickup.