How to change your forum avatar
The web forum displays a little picture next to each post, called an avatar. To change that avatar go to secretchronicles.org/upload-avatar, enter your user name and password (not e-mail address), and upload your desired avatar. That web page also allows you to delete your current avatar.
Your avatar must not contain copyrighted content without explicit agreement of the rights holder. It may not be sexually explicit and must not be insulting to other users. It needs to be in PNG, JPG or GIF format with a square size of 120 x 120 px or larger. You can also submit an SVG of square form, but please use a bare SVG and not one with vendor-specific extensions (if you use Inkscape to create it, save it as "SVG" and not as "Inkscape SVG").
FAQ: why no copyrighted content?
The US law knows a general exception called "fair use" that probably covers forum avatars and would make such use legal. But the TSC project's lead is based in Germany, and neither EU nor German law has such an exception. There are other exceptions, but none for forum avatars.
Tip 1: The best way to ensure your avatar is okay is to simply create it yourself. It's a good opportunity to learn how to use the great Inkscape graphics programme, which is freely available for all platforms.
Tip 2: You can also use pictures under CreativeCommons (CC) licenses. The Wikimedia Commons are a great source of CC-licensed material. If you do that, you can use your mail signature or Wiki personal page to give the required avatar credit.
The website README has the technical details of how to add an avatar to the main website.