Boy Meets a Yawning Tree
A result of playing with watercolour brushes in Photoshop.
Recipe: Go to Richmond Park and see lots of cool-looking trees (some oak trees there look very old and have fantastic shapes). Get excited. Make a rough sketch. Scan. Make a line drawing in Illustrator using a basic brush and the Width Tool to adjust line widths. Export to Photoshop. Make watercolour paper background and play with watercolour brush settings. Splash some (virtual) paint on and you're done.