Adapt the design of the Tor Launcher, Torbutton, ...etc and even the about:tor page to the new Firefox Photon UX
Photon UX guidelines are available here http://design.firefox.com/photon/ e.g.
- colors: http://design.firefox.com/photon/visual/color.html
- fonts: http://design.firefox.com/photon/visual/typography.html
To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information