Would be cool if you could pick a color and logo/design from the team vendor, but it should cost 2-3m like the other team perks. Buying the capes to wear can be cheaper like 1k-10k or something but to actually make a design for the team should be 2-3m
Would be a lot of work though, and like Kleio said, sprites are a pain xD Simple things like a + across the cape for flags like Sweden, Symmetrical designs like skulls, Partyhats, X's Paw Print, Halloween mask design could be done.
The real question would be how to make them really customized, the way sprites work in RSC is fairly primitive.