The plugin is requesting the extension 'http://axschema.org/media/image/default/'

It should probably either be:
'http://axschema.org/media/image/default'

Or:
'http://openid.net/schema/media/image/32x32'

Or both, and use the openid.net one if it is set.

Even when I modified my OpenID server to respond to the broken extension, I don't see where the image is actually being used.