Hello Creak,
Actually, the clutter is not a toolkit for drawing only. It allows you to create 2d/3d user interfaces using images that you provide.
Yes, you can display actors that have the image drawn at runtime, e.g. extract the Cairo context or use cogl. Some of good examples are available here:
http://github.com/clutter-project/toys
My suggestion to you is to choose, e.g. Cairo toolkit and create an image in memory, and then when the image is ready, simply copy it to the window (
https://developer.gnome.org/gtk3/3.0/gtk-getting-started.html search for Cairo).