In painting your portrait of any size -
I work very closely from ONE reference photograph.
A good photo is VERY important.
Long story short - the better the photograph, the better the final painting.
HERE ARE SOME KEY FACTORS THAT MAKE THE BIGGEST DIFFERENCE.

1. DISTANCE/ Movement - Perhaps the biggest mistake clients make is to send me photos that were taken of their dog running across the yard or perhaps rolling on their back, jumping for a treat etc. While these "action" photos show me personality - they are not something I can use for a portrait. Your portrait will be primarily of your pet's face and perhaps a small part of their body, therefore - you want their BEST FACE - the most flattering, well-lit, cutest shot of their beautiful face taken CLOSE UP or semi Close- up from 4 -10 feet MAXIMUM.
ALWAYS be asking yourself "Is THIS face/pose, lighting, something I would want in Portrait form?"
2. LIGHTING - if at all possible - take or send a photo that has been taken in natural light. NOT bright sunlight but natural light.
Avoid Flash photography. If you have the “LIVE” feature on your phone - use it - it yields multiple frames from which to edit.
3. QUALITY - The best Photos were taken with a good quality camera or phone which gets higher Megapixels will yield a better photo = better painting.
4. FOCUS - one “trick” I learned recently is to AIM FOR THE NOSE. Something about focusing on that feature results in a photo that does the best job capturing personality.
5. REMOVE - collars, clothing, and any other extraneous distracting elements from the photo. I generally do not include those items in the portrait unless specifically requested.
6. PERSONALITY - Each dog is a unique and wonderful animal. And YOU know YOUR dog and his/her quirks and special traits better than anyone. Try to capture those unique traits in your photos.
THANK YOU !