Hi @ReneCorbeil,
I'll move this over to the developers group, where more HTML-coder type people tend to hang out. In my opinion as a Canvas administrator, I'd probably caution against this approach a bit depending what areas you are trying to place this image in. it could interfere with buttons or other content on the web version, and I'm not sure it would easily work on the mobile version at all. You also may not be able to do this through the course tools (rich content editor, RCE)at all, but rather could have to use the theme editor, which is only available to Canvas admins and meant for more global changes. I've done some custom HTML things with the theme editor, but not in the RCE. I know the RCE strips out a lot of more advanced HTML, and this may fall into that category. Hopefully someone else will have a more definitive answer for you soon.
-Chris