Should we, perhaps, consider Metalink (RFC 5854)
instead of OpenGraph,
and any other similar solution which be specific to XMPP, for such task?
While I expect OpenGraph to be a popular vocabulary here because it is the
biggest standard for link metadata, we are not restricted to that by the
XEP.
TIL metalink, it looks basically identical to the jingle file element (and
the sfs file element). Sad that we now have three of these defined instead
of collaborating. However it's not really related to the main link metadata
use case.