I earned the event cosmetics, and here is my suggestion
Do not release the event cosmetics for everyone or put them in the store. Those cosmetics feel special because they were a timed exclusive that took effort rather than money to obtain.
However, I am not opposed to new players being able to get them. They should have to earn those cosmetics the same way we did.
I suggest annual events every associated holiday where the event cosmetics will once again be obtainable the same way they originally were and for the same amount of time each year. Timed exclusived that come back every year would be really cool to see in DbD.