But I discovered:

There is a command after you upload your sig pic.. it appears in blue. It says "insert signature picture".
You click on that and it puts the [SIGPIC][/SIGPIC] command in your signature, and it appears then in the big box that is above the upload graphic box.
Am I getting thru? It is hard for me to explain. If you see [SIGPIC] in your
signature box, the graphic should show up on your posts.

It is tricky, but I managed both the "mrsD" banner and a short text.
There is a limit however on size, and it is pretty small. Some of my earlier
choices were rejected. It took me several days to figure this one out.