What do you click on? Well can you make an engaging video? So banners and pics are easiest. All just a numbers game eg which of your adds banners work best on rotation then make a better ad than worst.
unique / Validity of who posted it / Reputation of who posted it / Social Engagement of others interacting ith it -> it doesnt matter what the form of media -> it could be a song , a video , a picture... a paragraph, these days people are smart... they can make their own inferences and such... and they can spot an advertisment a mile away...
You dont want to tell them hey buy this product...
You want to tell them hey check out this product and you can make your own choices... You want something that resignates with them... Maybe it's sentimental / maybe its visceral / maybe it's going to spark a sense of self worth or confidence ... You want to give just enough details that their brain can fill in the blanks -> You just give them the template for the "story"
Im talking kind of more of bigger picture marketing here -> My college years were spent focused on marketing / video production / alot of social media classes scattered in there too =) im no professional but thats the core thought process in a good ad these days... If you are interested i could send you some amazing reading material and even some stuff written by me if you wanted lol =)
edit* just to add one minor example
Think of the Enviornmental campaign surrounding that little girl who put up like a little monolugue video... -> Thats not selling anything particular other then an emotion... You dont care about iceland or whereever shes from... you might not have ever of seen the ocean or been effected by the coastal polution. But the video definetly had a major impact on getting people to think about something specific.