When I was a youngster, I used to doodle a lot. I'm sure my notebooks and papers were covered in doodles. Often it was fun to start with a squiggly line, similar to the one below, and then color in different patterns and lines in each section. This also worked for bubble letters. I even did an art lesson like this for Anna's class one year.
I still doodle some in my sketchbook, but mostly it is sketches. When I do doodle, it is usually random individual items, or the same thing repeated in a pattern, not a big integrated doodle. Terry posted some of her doodles on her blog one day (see here). That inspired me to do some integrated ones of my own. Here is doodle #1.