Re: lazy loading for images via css

A related standard proposal for HTML based resources can be found at
https://dvcs.w3.org/hg/webperf/raw-file/tip/specs/ResourcePriorities/Overview.html

Adding similar capabilities to CSS based resources, and especially
background images and fonts (mainly for icon fonts), can be extremely
useful for similar use-cases.

In the Resource Priorities proposal the 'lazyload' attribute is used as a
hint rather than a directive, and user agents should treat it as low
priority resource (and load it after the other resources), but may load it
regardless of its visibility (e.g. to avoid waking up the radio on mobile
at a later phase).
The only binding part in the Resource Priorities proposal is that
'lazyload' resources don't block the page's onload event.
It seems logical to apply similar rules to CSS based resources that are
marked for lazy loading.