I designed a Persona for Firefox, which is sort of like a skin for the browser that spices up the look of it. It's called Viking Grey and looks a little like this depending on your operating system:
If you use Firefox and would like to give it a try you can find it here https://addons.mozilla.org/en-US/firefox/addon/viking-grey/
While I was doing the Viking Grey design I was working on another from an old Celtic design but I couldn't get it to look good in the tiny space at the top of the browser, but I really like it and will use it for something someday.
I can't really take credit for the design, as it was originally adapted from The Book of Kells, so feel free to use it elsewhere if you'd like.