Walls have feelings too!
We have paneled the second room in ply wood, for a warmer feel. All our building materials are found disguarded - that's our rule.
The ply wood had been left for dead, after being abused by a building site just around the corner. Used as a fence around the site, the other site was painted in purple gloss with QPR graffiti in yellow spray paint. Each sheet had been attacked with a glue gun, and stuck to another piece. Then, as all the sheets were brutally pulled apart, the thin wood layers were ripped, leaving darker red layers underneath.
We spent two days, drilling around the wounds, sanding away the splinters, darning with linen and Herdwick, and cutting the sheets into 12" panels.