I doodle in a small sketchbook And I also use my machine to doodle for relaxation. I use cheap craft felt for my sandwiches. I buy packages of the 9"x12" size and put two pieces together then just doodle away. It is a good way to loosen up-- and it's very relaxing to just sit down at the machine and start Fmq without a preconceived idea + it's great training for those times when you've got an odd space on a quilt that needs to be quilted. The nice thing about the felt is you don't have to take the time to cut fabric and batting and baste a sandwich. I just put a pin in each of the corners to hold the two pieces together.
Rob