A friend of mine calls these "inklins". It's a form of doodling that's very addictive.
Recently she suggested a swap, and these are my contribution to it. Each "inklin" measures 4 x 4 inches. They've been doodled on watercolour paper, using a Pigma pen. Two of the backgrounds have been coloured using a watercolour pencil.
The second bookshelf
13 minutes ago