Image is of my personal OC Crescent Jade in some purple night armor. The silver markings/tattoos I borrowed the from look of from NCMares' Twintel image: https://www.derpibooru.org/images/1323368
That image was, of course, fanart of N00813's FIM Fiction story Schemering Sintel. You can read it here: https://www.fimfiction.net/story/59880/schemering-sintel
How exactly those tattoos/markings integrate into a pegasus versus a unicorn? I haven't decided yet.