I also am doing a magazine advertisement for my game.
I have bought a couple of magazines and researched how they design the advertisement. Many magazine advertisements use the cover of there game, this is a good idea because then people will recognise your game more easily. They also have the game case on several different consoles to show the range when the game is closer to its release date. There are also advertisments that don't show the cover. these are more extravigate then the ones that use the cover. This is used to attract people to the game. Advertisments sometimes use screenshots of there game.