From SA-MP Wiki

Adding ALL Skins

Below an example on howto add all skins:

IsValidSkin By: Simon

IsValidSkin(skinid)
{
    #define	MAX_BAD_SKINS 22
    new badSkins[MAX_BAD_SKINS] =
    { 3, 4, 5, 6, 8, 42, 65, 74, 86, 119, 149, 208, 268, 273, 289 };
    if (skinid < 0 || skinid > 299) return false;
    for (new i = 0; i < MAX_BAD_SKINS; i++) { if (skinid == badSkins[i]) return false; }
    #undef MAX_BAD_SKINS
    return 1;
}

public OnGameModeInit()
{	
    for(new i = 0; i < 299; i++)
    {
        if(IsValidSkin(i))
        {
            AddPlayerClass(i,0.0,0.0,0.0,0.0,-1,-1,-1,-1,-1,-1);
        }
    }
    return 1;
}