We fixed horizontal battens and thin sheets of ply to the walls.  All this was then cladded over with thin pine boards to give the van a more homely feel.  We sanded and stained the cladding with Danish oil for a nice finish.  We managed to find a whole load of laminate floor boards in a skip.  After a good clean up I simply cut and laid them down to fit.  However, we might end up changing these to a vinyl floor at a later date to save on weight.