Update from James Gunn:
The photo you see above was shared by Nathan Fillion and it features a scene he was in that was cut out of Guardians of the Galaxy Vol. 2. The image came with the following note from the actor:
"From a scene you won't see in Guardians of the Galaxy Vol 2. Is the movie still spectacular without it? Yes."
Fillion looks absolutely hilarious in his space barbarian-looking costume. There was a rumor that Fillion was supposed to be playing Simon Williams aka Wonder Man in the film, but this photo doesn't really line up with that rumor.
It looks to me like he was just some kind of space barbarian, which is still cool! It's a shame that his scene was cut from the film. At least we have this fun image to enjoy!