We saw this same christening photo used for Princess Charlotte's Christening reply. This is not the 1st time they have sent the same photo on two replies. Last year, Harry's Birthday and Christmas reply used the same photo and so did George's 1st birthday and Catherine's announcement of her 2nd pregnancy.
The Cambridges choose not to use the Christmas picture they released last month, on their reply. It's likely that the Cambridges hadn't released the photo yet, when they started printing and sending out notes for Christmas. This is very often a problem for them. George's birthday replies both, this year and last year, didn't use the photo they had released for his birthday, rather using an older photo.
We still have a bunch of Christmas replies we are waiting on, I would expect we will be waiting for replies till the end of this month, or early next month.
I looked back at my christmas replies from last year, the last one came in March. It was from Denmark. They have a pretty great response time in getting their replies out, but the Crown Prince Couple usually sends their replies economy which means it taken for ever to arrive. Some times up to 45 days in the mail.
2015 Christmas Replies (Bottom of Page)