Here's a quick mockup of what it could look like either in the message header or by the signature.
Personally, I think I like the one by the signature better, as it both lets it be larger and fits with RP better (the character affixing a coat-of-arms to their message next to their signature). But I'd like opinions.
(Edit: Hm, it looks like the way I posted the image will expand nicely inline, but then not show you the full width unless you scroll sideways. Weird. Sorry.)
