Update: We've got it identified. It's a gown that Taiwanese singer Mei wore to a New Japan Philharmonic Performance by Joe Hisaishi. Well done to Jasonjayr for sleuthing this one out!
Here's one of those frustratingly amazing, but impossible to identify Tumblr finds: a gown with a long train, decorated with the skeleton of a mighty dragon with a barbed tail. My Tineye and Google Image reverse searches just turned up a bunch of people saying, "Hey, that's great, who made it?" and NO ANSWERS.
Do you know? Post in the comments.
I'd also be interested in hearing whether you-all would be interested in participating in a weekly "Figure out who made this amazing, identifier-free thing I found on Tumblr" post? It'd be nice to get some attribution for all that unattributed awesome out there.