Half of these symbols are MEMES.

Narwhal + Bacon https://knowyourmeme.com/memes/the-narwhal-bacons-at-midnight

The Shiba dog https://knowyourmeme.com/memes/doge

Cat pictures were a big thing in early reddit https://knowyourmeme.com/memes/subcultures/cats

The Cake Is A Lie https://knowyourmeme.com/memes/the-cake-is-a-lie

The costume partiers are probably dressed up as specific characters. One of them is obviously Captain Falcon. That may be a Sailor Venus and a Sonic next to him.

The Illuminati pyramid at the top of the upvote arrow may be significant.