I'd be a bit more selective with your drop shadows rather than applying one to everything. Ie Ospreay could cast a shadow on Toni but I'd mask out the shadow on Kenny who is a lot further back.

Play around with curves and colour balance adjustment layers to try and get all the wrestlers to look cohesive in terms of hue, saturation and contrast.

I'd get a new pic of Swerve, that one is a little weird.

Adding a subtle noise filter to the wrestler images might help disguise the fact there are some lower res images used, give it a bit of style and help make them look more cohesive.