We should add a feature to allow getting images from an image-resizing proxy. At least for now this would be an about:config option for individual users, OEMs, or mobile carriers to reduce data usage. We should allow a URL to be set for a pref named something like "network.proxy.images". If a proxy URL is given we would detect when an incoming image is larger than necessary for the current situation (device or page) and communicate the image URL and a desired size to the proxy. The proxy would then return an image that is sized appropriately.
It may also be worth doing loss-less optimizations (https://gitorious.org/fmarier-misc-scripts/user-scripts/source/optimize_images) inside that proxy.
one of the more standards-y things from chrome makes more sense.. client hints or low bandwidth