Bets.io also has a couple of bonuses going on though they are not Christmas themed;
cashback every day
Weekend reload bonus
first deposit bonus
mystery boxes

If you are a frequent gambler, I would suggest you take advantage of the free bonus. The cashback everyday bonus sounds interesting as it gives the player a percentage of the amount deposited. The catch is you would have to deposit a high amount of money to get a higher percentage. Read the TOS for further information to make sure you qualify.