A lot of the time the reason a photo is not sharp enough to use is that the original photo has been taken from a long way away and we have cropped it down to just a head pose. To avoid this problem make sure to take some photos of your pet where you just stand about 2m away and zoom in and just take their face.Those photos will be nice and sharp if you ever want a portrait done ( assuming they are taken in bright light without a flash).
Don't be put off by all this I have created lovely portraits from blurry photos it's just that with a little planning you can have nice sharp flattering photos that will give a much better portrait.
If you are local I can come and take suitable photos.