I love the pose on Umbreonage's sprite, and the back shinies don't bother me much. It's the best of the three in terms of pose and attitude, without being overly complex and crammed-looking.
HeaLnDeal's sumission also had a cool pose and went for a unique shiny pattern, which emphasizes the "false face" or the design in a clever way, probably the best case of this amongst the final slate.
Quanyails also make a near-perfect sprite, as always. Despite going full-ham on the tentacle spikes, the final look is remarkably smooth and I think the pose is spot-on for a menacing vampire squid.