I used this as a sample:
http://www.simplythebest.net/info/dhtmscript52.html
You can check out their other samples, too.
I was able to customize quite a bit, once I figured out where. I saved it as a JS file (there's 2 of them actually) and saved them on the domino server under the domino\html directory, so non-domino users could modify them. To reference them from the pages/forms, add a "/" to the src=
(i.e. in their code it says src="coolmenus4.js", but I had to change it to src="/coolmenus4.js")
Finally, make sure that the mapping in the Directory does map html to whatever directory you put the js files into on the server.
This does not use graphics, but it does "float" with the page and this may be annoying (esp when printing pages). There may be a way to make it static, but we didn't do that.
Good luck.