[Jeffry]

At TOP of your GM:

pawn Код:

new MyRandomSkins[] =
{
    0,
    3,
    12,
    55
};
//The last number must not have a ','.

Just add the skins you want.

At OnPlayerEnterCheckpoint:

pawn Код:

SetPlayerSkin(playerid, MyRandomSkins[random(sizeof(MyRandomSkins))]);

Cheers!

PS: Have a Marry Christmas and a Happy new Year!