Yes, those who are camera shy can have a message on their tile. No, you cannot have a picture created on the tile from a photo.
I checked into this because I wanted to surprise my parents with a tile. What I did instead was give them (and dear friends of ours) tiles with messages on them. They received a nice certificate in the mail with the location of their tiles. Our friends, who will be taking their 1st Disney trip in April, are very excited to find their message at Epcot. My parents will have to wait another year!