I have messaged the seller and I will see what she comes back with.
18 x 18 would work for me - just center it on the back. What is the fabric? How will it wash? Have you considered a picture of the dog? My son's quilt has a picture of his daughters on the back and it is washing just fine. And that boy is a frequent launderer who over dries things. He does use cold water.
I have seen quilts where people put pictures on them - so I did think of that. When I have printed my own labels they are not soft (at least they way I tried). Are the custom pictures on the quilts soft?
I like the idea of it being on the back so its a little bit of a surprise. They will look at the quilt front and think that's it and then surprise the puppy will be on the back. I like quilts that have interest on both sides