Good Reference Photo Tips
1. Frontal or 3/4 angle face picture usually work the best.
2. Use photos with good illumination
3. Make sure the subject's face is not cropped off or missing features like the hair.
4. Avoid using dark or blurry photos.
6. I can can always mix and match multiple photos build a good likeness.
7. If you have the multiple people, everybody doesn't need to be in the same reference pictures.
Sample pictures are as shown below.