... Agreed! I would buy a Crystaline Entity ornament from Hallmark, gladly! And it would be my first - and only - relating to STAR TREK, especially if it weren't obvious about its STAR TREK origins. Just the entity itself, with a hook on it, is all I'd want.
^I did once see a custom Crystaline Entity ornament by a fan that looked exactly like the one in TNG. They used several intersected snowflake ornaments they found in a Christmas store. Not this one, but similar method: http://seawave.squidge.org/customtrek.htm
Hallmark intended to offer an Excelsior Class starship ornament back in the 1990s, but it was too problematic to get the lights to work. At the time, UL requirements had become so strict (for the corded ornaments that plugged into light-string sockets) that the ornament would have been altered in ways that were inaccurate and unappealing. Since 2005, all the ornaments have been battery operated, so it's likely that an Excelsior Class ornament will be back on the list of candidates to be issued at some point in the future.
Not a Hallmark ornament, but one of the Christmas ornaments once offered by the Las Vegas "Star Trek Experience" was a very cool blue-shirted Spock playing his Vulcan lyrette! I had bought a batch of Star Trek Experience ornaments (Talosian, Mugato, Gorn, Spock, Picard, Cardassian, TNG Klingon, Borg, Quark, Neelix) second hand from a penpal. I realised I didn't need the Spock nor the Picard, since they were already well-represented by Hallmark ornaments. I added a halo and wings to the Spock, to make a unique tree topper angel but, about a year later, I realised he'd be even more accurate in his ST II outfit. The black belt is a twist tie that attached him to the tree. A little wine and white paint and he was done: Spock angel by Ian McLean, on Flickr
Weird - I see the Uhura and Wrath of Khan ornaments on Amazon but nothing about the Enterprise-C yet.