You can now get the 10 year anniversary outfit in payday2 by logging in, pic related is the outfit
You can also get a really cool looking Jester mask by visiting their site and clicking on their "gleam" link: https://www.paydaythegame.com/10th/ it will generate a steam code for you, then you just activate it in steam to get it

Special event game mode is also live until October 28th, when you kill special units they'll spawn balloons which you can pop for bonuses:
>Shields
Armor regen buff
>Taser
Refill ammo buff
>Medic
100hp buff
>Cloaker
Double damage buff
>Sniper
Infinite ammo buff
>Dozer
God mode buff