This demo tackles designing scenes in 2 point perspective. The final image is going to have a lot going on, here, we start to figure out and shape what we want to spend a lot of time on later. The whole purpose of thumbnails, or as I like to call it: booger sketches, is to weed out poor ideas and setup something worth committing to. At this stage we're not worried about all the technical stuff that slows a drawing down, though the better you are at all the technical stuff, then you can use this stage of design to work out a ton of technical issues that you will be facing later in the process.