If the images are specifically under the GPL it's hard to tell if using the images would be considered "mere aggregation" or not. If you incbin them then you're definately in violation. If you simply provide them with the app/game with the option of using a different set, you may be in the clear.
I don't know the exact situation, but your best bet is to contact the author and ask if they'd be willing to license them under another license so you can use them. Some image files actually include copyright information in their metadata, so that might be worth a look too.
I think a lot of the vitriol over the GPL comes from people who don't understand that it's actually a license that gives you rights. If it upsets you, you have the right not to use it or write your own or buy an alternative.
I don't know the exact situation, but your best bet is to contact the author and ask if they'd be willing to license them under another license so you can use them. Some image files actually include copyright information in their metadata, so that might be worth a look too.
I think a lot of the vitriol over the GPL comes from people who don't understand that it's actually a license that gives you rights. If it upsets you, you have the right not to use it or write your own or buy an alternative.