This would make for an amusing tattoo. I love how you designed King Sombra and the background amusingly somehow pushes him forward despite being pretty dark colors themselves. My only quip with the picture is that the black smoke seems lost in the background and does not add much appeal to it though I can understand why this approach was taken.
IIRC, a fuzzy purple googly-eyed creature was seen escaping the Crystal Empire just before this happened. Still, it didn't look like the Crystal Empire had a lot of agriculture so he still would have been enraged to find no cold milk for his cookies.
Very bold and powerful expression, and he exudes so much viciousness and anger as he stops to gaze upon the target of his wrath. Yet the fade of his mane and cloak towards the back implies that he's a force in and of the violent wind itself. That face is amazing, and the rest of his strong body, that very scare looking collar (for splitting walls probably!) and that nasty looking horn are all powerful imagery. Sorry to hear you won't be doing more like this. (And for that, I'm not going to spend a paragraph making fun of his name. )