Move static images for legacy from theme to global

[mattstratton]

See 2016 Atlanta talk page for example.

[bridgetkromhout]

This is the one blocker left for the release of the responsive site, from my POV. If we can get this in tomorrow I'd be in favor of getting the responsive design branch merged in.

[bridgetkromhout]

For posterity, this is what the issue looks like:

And after correction:

[mattstratton]

Fixed by 71dc15d