Skins with progression.
So, I noticed that Depth (not a commercial) had an update where it featured a skin that can be upgraded by killing divers:
How about the same thing for DbD? You buy a skin in the store and then you have to complete some goal in order to unlock different styles of that skin. In case of depth, it is some kind of corruption that progresses the more you kill. I think having something like that in dbd would be awesome.
For example, it could be used with Blight skins. Base skin features the syringe in killer's back and little symptoms of Blight spreading, the more you kill/do something, the more blight progresses until it reaches the final form which is blight skins we are used to.

Comments
Progressive skins sound fun!
Although they would probably be sold as full sets. Meh, having a skin that you could change to a specific version/it changes mid-game would be neat.
I wouldn't mind such skins being sets, honestly