The four types of magazine covers

Image based magazine covers are the most common approach. It has one or a few people on the cover and its posed so the person is looking at the photographer. The plain background of this gives an advantage because it draws more attention to the person, which is normally a celebrity that causes more people to buy the magazine. 

Illustration based magazine covers usually represent something funny or unusual. They have an animated drawing for the cover that wasn't photographed.  This type of cover has been used since the 30s and famous magazines like the New Yorker often use this. An advantage would be that it is sometimes easier to get the point across using this one because it can show symbolism and metaphors and things that can't be captured on camera. 

Type based magazine covers have text as the prominent part of the cover. This is not as rare as illustration based. It usually shows something shocking and powerful. It has an advantage because sometimes words can be better at getting a message across. They are increasing in popularity. 

Concept based magazine covers can be all three of the previous approaches combined. They have to be understandable by almost any crowd, and they get the point across quickly. This's usually shows up in business magazines.