Set an image as your desktop wallpaper in Google Chrome
Still, it's a bit more than I wanted. Give me a simple right-click, set-as-wallpaper option. And that's precisely what Mohamed Mansour has done. Witness: the Set image as wallpaper extension for Google Chrome! Right click, set image as wallpaper, and an HTML5 previewer appears so you can eyeball the finished product -- you can even choose to stretch, center, or tile your image. Future versions will include an options page that allows you to skip the previewer and simply perform a two-click image swap.
Unfortunately (or fortunately, depending on which OS you use) Mohamed's extension currently only works with Windows. Linux and Mac versions are being worked on.
By the way, there's absolutely no need to panic over MG Siegler's comments on TechCrunch that "someone fed the bloat trolls." Set as wallpaper only uses about 5MB memory -- the same as most other basic extensions. Clearly MG thinks that saving an image, locating it on disk, and then using OS X's built-in controls to set the wallpaper is a much more elegant way to do things.
As for me, I'll take my context menu enhancement, thanks.