Install CPL's Chrome theme for an stylish, unobtrusive way to show your support for CPL.
Like the Firefox Persona, the Chrome theme design centered on being unobtrusive and using the space effectively.
The Chrome theme guide explains the huge number of ways you can customize your theme. This gives a lot more flexibility compared to a Firefox persona, but also makes creating a theme somewhat more difficult and time-consuming.
Chrome theme images are left-aligned for the most part, so the putting your most important graphical elements to the left ensures they will appear in your design. Since the "frame" gets obscured as the user opens [tons of] tabs, the real graphical canvas is the "toolbar".
The back, forward, and reload buttons appear in the toolbar, so the graphics should be understated enough to keep those buttons usable, with contrast provided by sound color decisions in the manifest. More-distracting graphics can appear in the frame, as they'll disappear as tabs get opened; just be sure to color and tint the tabs so they always have good text contrast.
It's important to thoroughly test your theme, including incognito mode. If you have access to multiple platforms (Windows, Mac, Linux, Chromebook), testing them can also be useful. New tab page graphics, for instance, should scale for a huge 27" iMac screen. Button tints can sometimes look different across platforms as well. Also, keep your finished theme installed after you're done; if you don't want to use the finished product, chances are other people won't either.