Name the image after your userid, i.e. userid.jpg . Note that a quality level of 85 may corrupt some computer graphics images. Use 90 or even 95 if you feel it's warranted. Use the same filenames as above, but use .gif as a suffix. Try to keep as close as possible to 100x100, or 10000 pixels if your source image is not square.
Smaller images are incomprehensible, but larger ones take too long to download.
Some background information and documentation. This can range from a plain text description to an HTML page. You may want to include the Tcl script used to create the scene. If you use HTML, you may include links to your images, just be sure to label everything with your userid and use relative links. Say whether multiple images all should point to the same documentation, different documentation, or different parts of the same documentation.