abstract algae background bacteria bacterium bog canal environment environmental fen goo gooey green grunge grungy lake marsh mat nature plant poison poisonous pond scum Slime slimy stagnant swamp texture thick toxic water weed wet appearance backdrop coloring colors colouring colours cool decorative density ferns flora foliage fronds garden greenery horticultural horticulture light light-green lighting patterns plants shade shapes spread spreading sunlight textures variation vegetation wallpaper Australian reflecting reflection shadows