The photo is the same as his Birthday Card, a pic of him during Walk of Britain, with Walking With the Wounded. (He did this with his previous Christmas & Birthday reply in 2014 as well, using a pic from Invictus Games for both).
Another interesting note, is Harry's Christmas and Birthday replies both this year and last year featured pictures by Chris Jackson.
The message on the card is the same as last years. Which is fine, I do like how the wording is slightly different than the Cambridges and Charles and Camilla's reply.
Weird, that once again we aren't seeing the pic that Kensington Palace released for Christmas. Which was a black and white version of the picture below. I understand they are using them for their Private Christmas cards, but it seem odd to me that they would release the pictures to the public, but not use them. Normally, There is a issue of not having the photo released yet, when they are printing the replies, but the picture below was released back in September.
Prince Harry's other replies