To add to what Facemaker said, there are a couple of ways to include images.
There are a ton of character portraits already available. However, if you can’t find something appropriate, you can submit them. More info is here, although I think submissions are on pause right now:
link to a message in another game
Another way is to find a picture you want to use, host it on a site like Imgur, and include a link to it using this code:
<img src=URL of your picture here>
Here’s an example:
<img src=https://i.imgur.com/7vjvokB.jpg?1>
This message was last edited by the user at 16:35, Fri 04 Oct 2019.