It's not Sonic. I've already been contacted by someone looking for similar advice on the image, and it was discovered that it's not from Sonic at all. I'm not going to tell you where it's actually from though. That'd be cheating.
I'm afraid I'm not willing to give anything away. The team who contacted me told me what they'd discovered in confidence, since I was curious. I'm not going to give away their answer, seeing as I didn't even play any part in finding out where it was from.