It also allows you, as a gift-giver, to seek out a style that reflects the recipient's personality and tastes in some way.
Individual certificates could have been signed by the gift-giver, or a group card may be given.
A quick couple of sentences that lets the gift-giver know that you do remember which gift is from them--and why you love it--will suffice.
In that case, keep the tone light and not as informal as you would if the gift-giver was your best friend.
Our gift-giver Father Christmas or Santa, derived from the Turkish St. Nicholas, the Dutch Kris Kringle, the French Pere Noel, the Russian Babouschka, and the Italian La Befana.