With the Xbox Series X coming about I think the Xbox 360 marketplace and all its goodies will one day be defunct. I didn't want all the content in the themes to become lost media. So I purchased all the ones officially by Rare, extracted all the textures/images. I put them on archive.org so even if Xbox 360 marketplace shuts down, we don't lose all this stuff.
https://archive.org/details/rare-themes