From the Super Mario Wiki
An Emblem is a symbol that appears on a kart or bike in the Mario Kart series. The emblem in Mario Kart DS, is customizable, but in other Mario Kart games, they are character exclusive only. In Mario Party 7, whenever a character places an Orb, it creates a Character Space which is symbolized by an emblem. In Mario Party 8, an emblem appears next to the character to indicate when it is the character's turn. Also, when someone owns a hotel in Koopa's Tycoon Town, the emblem will appear on top of the hotel to indicate that the character owns it. In the minigame Stampede, the player must stamp his or her emblem onto blank sheets of paper.
Emblems also make an appearance in Mario & Sonic at the Olympic Games and Mario & Sonic at the Olympic Winter Games. The symbols appear on flags and Emblems (not the symbol itself) in these games. The Mario characters do have their usual logos, but since all Sonic characters except Eggman do not have an emblem, most have a one-colored silhouette of themselves at a different angle with a colored background.
When not using a customized emblem:
When using a Roadblock Orb:
Rackets of unplayable characters and items can be accessed in the game.
Mario Kart DS
Mario Party 7
Mario Party 8
Mario & Sonic at the Olympic Winter Games
Mario Kart Wii
New Super Mario Bros. Wii
Mario Kart 8