Promotions is a 4chan meme centered around posting NSFW images on work safe boards. It originated as "I GOT FIRED!" implying the poster was fired for looking at porn at work, this was followed by the stock response "I GOT PROMOTED!"(implying they were taking over the other person's position). Eventually people stopped saying "I GOT FIRED" and the phrase "I GOT PROMOTED" was shortened to "PROMOTIONS!". This is probably due to the fact that all 4chan memes eventually become races to see who can post them the fastest in the right situation (see in b4). Promotions is often accompanied by a black man holding his hands out(seen right), or different people/characters in the same pose.
Many new users think that posting porn will get them promoted because a boss would be pleased by seeing porn at work. These people are most likely underage B&.