This was a project I did for a DeviantART group Swirly Artists, called the Endless Doodle. Each artist continues by building on the previous image and then develops his doodle freely. The progression looks quite nice, so be sure to take a look at the link.
Brush pen, watercolor and colored pencils on an A5 Winsor & Newton sketchbook.
Here's just a pure ink piece:
I would have probably left it like this if it wasn't a part of a project, but I was continuing from a doodle that had some bright colors in it, so leaving my own part black and white wouldn't make sense.
On a different note, I'm really terrible taking on projects like this while I have piles of work to do.