My idea is paint brushes and paint in minecraft. Now you might be thinking doesn't ink and dye already do this, but can you paint wood and other blocks like that yet. Notch would have to make a new material called hair that you would get from cows, maybe 1 hair every 3 cows or so. You would also need to make paint which would be made with a bucket of water and the color ink you want the paint to be. You would be able to paint wooden planks,smooth stone,beds(maybe),fences etc. But NOT wool as this would defeat the purpose of dye.
Crafting
Head for brush
Red wool= hair
this would equal one head for the brush
Crafting
Head for brush
Red wool= hair
this would equal one head for the brush
paintbrush