all riot needs to do for kindred loading screen splashes is to use an altered dual mask image.

just like this http://2.bp.blogspot.com/-ooInvgdxL4M/Vfi_c6hUedI/AAAAAAAAxYk/cRkNCeM7tRc/s1600/Kindred_Square.png

now they just change the mask shape and colors to match those of the skins

or they can make splash arts that can include both champs in such a small space.