itunes comes with a limited number of pre-defined genre images aka badges. Some of these images are associated with more than one genre, e.g.
Alternative is connected to Alternative, Alternative & Punk, Alternative Country, Alternative Folk, Alternative Metal, Alternative Pop/Rock, Alternative Punk, Alternative Rock, AlternRock, Punk, Punk Rock, Punk/Folk, Punk/Folk/Reggae and no doubt many others that aren't represented in my library. The dance image is linked to Dance, House, Techno & Trance or genres begining with those words.
If there is no default icon for a particular genre then itunes will display a cover from one of the albums with that genre. If you run your mouse pointer slowly across the image from one side to the other it will change to display the covers of each of the albums in that genre in turn. You can right/option click on any of these to *Set Default Grid Artwork* and that image will then be used to represent that genre. Use *Clear Default Grid Artwork* to reset things.
If you want to add your own custom genre badges, using artwork that is not in your albums, then place the images you want to use in the folder *C:\Program Files\itunes\iTunes.Resources* and edit the file *C:\Program Files\itunes\iTunes.Resources\Genres.plist* using something like
Notepad++ to connect the required genres to your new images.
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