Can't say if they would be a good idea and work for an RV backsplash, but CAN say that we used peel and stick tiles for kitchen floor in house more than 15 yrs ago. All the comments on line were to not use them, they wouldn't last!! Still on floor, still look almost new, and no complaints!!
They were installed on 1/4" plywood underlayment, and I used a primer made for adhesive flooring on install. On an RV wall, which is usually thin plywood with a paper or vinyl covering, maybe the primer would be a good, maybe necc item to use. The tiles we used were imported for Lowes from Italy. Can't say anything bad about them. Noticed last trip to a Lowes, that peel and stick seems to be resurging in the home improvement area. Many, many choices!!