[Konstantinos]

Let players select their skin on the skin selection if they're going to register and insert into the database the default value as '0'. Then on spawn, get player's skin and insert the new skin id.

Also, about the players who are already registered, let them select their skin too and check on spawn. If the skin is 0, set the saved skin, if the skin is not equal to 0, let them spawn with that new skin and insert it on the database.