It would be great if we could have charcoal sticks that could be used to place one of four black directional arrows on a vertical surface. Up, down, left or right.
Perhaps crafting them by placing wood into the furnace just like we do with ores... They should have a usage limit: 20 uses? This would be invaluable to mark the way out of a cave or be placed on block stacks out in the wilderness to lead you back to camp.
Or... 
perhaps you introduce chalk(limestone) into the mineral table.
Besides drawing white arrows, Chalk could also be used as an ingredient in whitewash (paint). Whitewash is made with lime, salt and water. You can color it with various pigments to get other colors. Then with wood and some animal hair we could craft brushes (and a bucket) to paint arrows or blocks.
