Images like these have inspired me for a long time. I have always been fascinated by Sir Lawrence Alma-Tadema's random blocking in of flat shapes of color and rendering out other areas almost to completion. Included is a photo of Tadema at his easel, with an unfinished painting that recently went up for auction (painting is the following image)
I love imagining I could walk up and look at what was on his easel; these are not all the known unfinished paintings out there, but some of my favorites. Enjoy!