Best wall covering for my van build?

[B and C]

My old vans I just used 1/4" plywood.

 

[andi]

I'm looking into low VOC self-stick wallpaper over low VOC insulation boards.

 

[CosmickGold]

my mistake, I was used to their former classification as plants and did not realize the scientific classification had changed.

Yeah, I used to think they were plants, and only recently learned of the classification change. There is mention of this change in the Biology Dictionary, which in part reads: "In the early years of scientific study, fungi were part of the plant kingdom. Since that time they have been given their own kingdom because of their unique structure and function. . . . One of the main differences between plants and fungi is that fungi have chitin as a component of their cell walls instead of cellulose."