Usually, you only see art of the main charas. (in just about ANY media/comic/toon/anime/etc.). But this has to be the coolest art of "supporting" charas.. And each Rubies' personality is showcased in their "own pic", as if they could stand in their own art pieces each.
Reminds me (symbolically) of their ability to fuse, and the diamond frame drops their homeworld(for now?) allegiance.
COOL S.U. art.... of the Ruby Squad!