abstract appearance backgrounds bark brown bumps close-up colors colours cracks edge edges layers patterns ridges rough shades of colour smooth strips surface surfaces texture textured textures tree tree trunk trunk uneven variations varieties wallpaper wood Australian melaleuca rhaphiophylla melaleucas myrtaceae paper-like paperbark peel peeling useful background bare cracked dry eucalypt eucalypts gray grey grooves lines mottled self-shedding shadows shapes shedding sunlight