Does anyone know why new images in BP Ed Draft are getting 404'd?

All- Simon helpfully added a couple of images to the Spatial Things section
[1] to clarify some points. Unfortunately, these aren't being served by
GH-Pages. Works fine on my local version.

Anyone know why? Is it just a quirk of GH-Pages?

Thanks, Jeremy

[1]: http://w3c.github.io/sdw/bp/#spatial-things-features-and-geometry