When it comes to choosing photos, the most important thing I look for is clarity. The best photos are ones that aren't extremely pixelated when you zoom in and you can clearly see your pet's fur. While it's not always possible, please keep in mind that the more details your photo has, the more details your drawing will have.
Please choose clear, well lit, close up photos that showcase your pet's personality and avoid harsh lighting, blurry movements and screenshots.
Also, if you would like multiple pets in your portrait and don't have a good photo of them together, individual photos with similar lighting is ideal.