Ok look I don't have the time to go deep on this at the moment but just quickly this is what I have got, which will include some duplicates from what others have already knowledgeably posted.
(1) The Reebok logo is a pyramid with a shining capstone (you are looking from above). It also looks like the laser sight from the Predator films; I don't know if that is significant.
(2) The previous sponsor, Monster, its logo is 666 in ancient Hebrew numbers.
(3) I have read on the internet people saying that Dana White often does the devil horns sign (cornuto). I don't watch him on anything, so I can't say but the only picture I could find of it is this, which has obviously been altered. If anyone has the original, or another one of him doing it, please post. Here is a sinister cover pic of his mother's book as well.
(4) Benson Henderon is not in the UFC any more but he used to and presumably still does throw up the trapezium / diamond Masonic sign all the time. His gym also uses Masonic symbolism.
(5) I remember seeing a picture of Rousey doing the All Seeing Eye / Eye of Wisdom / Eye of Horus etc. post covering one eye. I've not been able to find it, again if anyone has it please post.
(6) Bryan Barberena chucks up a trapezium sign.
(7) It is a possibility that at 13 seconds on the 13th of December Aldo threw his fight with McGregor, whom we have touched upon above.
(8) Here is Joe Rogan doing the cornuto with Stanton LaVey
(9) More 'diamonds'