I use GIMP to illustrate many of my projects, but one thing that’s seemingly difficult to do is draw a circle. I don’t have to point out the benefits to using this “feature”, so here is the video tutorial that I made:
This “border selection” technique illustrated here can also be used with the “square select” or “free select” tool to draw a square, rectangle, or whatever shape you like. I used the “bucket fill” tool on the middle of these shapes as well as the borders.
Not exactly a Matisse, but you get the point. If you want to illustrate a project, drawing circles or squares around something you want to highlight would be essential. Check out my other GIMP tutorials, especially this one about dimensioning your projects using layers.