When the TN isn't derived from the OBJ, we're wasting storage by adding the "folder icon" default thumbnail to every object as a TN datastream. Instead,
- each solution pack should come with a default thumbnail for each content model it defines (as is currently the case)
- these defaults should be configurable by content model in the admin interface (so they can be updated/replaced)
- TN datastreams should not be added to new objects by default. Users should be given an option to upload a TN of their choosing in the ingest steps. Users can add/replace the TN of an existing object (as is currently the case)
- if the TN datastream is not available, the display should use the configured default image for that object's content type.
- the Regenerate Derivatives call should not change user-uploaded TNs.
Warning: it's been customary to use islandora/object/PID/datastream/TN/view in many places, such as Views and Solr search results (and more generally, any time an Islandora object is displayed or referred to it's assumed that it has a TN datastream). If we do what's suggested above, these would break. I think it would be desirable for this Drupal path to resolve to the default TN if the datastream is not present. I'd be tempted to change how Islandora's menu callbacks behave, but am wary of making what is essentially a change to Islandora's API.
Split off from