Not a particularly exciting idea, but I would love to be able to give my nichelings rosettes
It would be an allele of the pattern gene. It would add to camouflage in the savannah biome. Different shapes could include rosettes with and without internal spots and elongated rosettes
Pictured below, from top to bottom, is a leopard (rosettes without internal spot), a jaguar (rosettes with internal spot) and an ocelot (elongated rosettes)