One thing I always praise about Arknights is that they have fashion brands in their game, so you know which skins has which theme, and belongs to which brands.
"Icefield Messenger" is always themed about Christmas.
"Marthe" is akin to Nike or Adidas; sports themed
"Bloodline of Combat", my favorite, is when an Operator is at their prime. All of their skins are so, so beautiful it gives me goosebumps.