I don't think he understands how ridiculous it is to see a grown man dressed like that in a solo photo, if he were dressed like that in a party situation or something and there were other people in the photo with him it would be acceptable, shit there wouldn't have to be other people just signs of a party like some booze or decorations or anything like that.
Even assuming he wasn't at/going to a party and was going trick or treating with any young cousins or nieces/nephews as part of a family outing you don't get someone to take a photo of you, the ADULT, dressed as a character from video games aimed towards children.
I think the photo really supports what people have been saying about how he's stuck in school, even the way he's posed is like something a kid would do when their mum takes a photo of them dressed as a super hero or something.