Now I know how wonderful that standard motorhome wall treatment really turns us on but here's a way SOME of you might save your valuable heat.
You're looking at that wall treatment and want to cover it over.
This is what you do.
Before ever putting up one sheet of paneling, line the walls with a FOIL barrier. You can do a search for the material on the internet. Not ALUMINUM FOIL, it has to many impurities and won't have maximum effectiveness.
What the heck, here's where you can buy:
Radiant barrier reflective insulation - radiant barrier qualifies for 30% tax credit
So you have the foil stuck on the wall, next you add 1/4 " to 3/8" furring to the walls vertically over the foil.
Install your paneling with the furring strips you installed maintaining that air gap. The thickness of the gap is not important. Just as long as there is an air space behind your panelling.
You can cut you heat loss by 50% or more through the wall.
The FOIL BARRIER reflects back the radiant heat trying to excape through the wall.
It's better than buying an electric heater and your motorhome will look great commensurate with your skill level. I'm not giving lessons on trimming it out etc.