Straight on images that look just like you. (If an image looks a little off or the angle is wrong then you could get a model that doesnt look quite like you. Its better to upload 4 images that look exactly like you than 8 than that don't)
Shoulders-up or waist-up
Good lighting (no harsh shadows)
Variety: different days, outfits, hairstyles
Models looking at the camera; eyes open, natural expression
Do not upload images that include:
Other people in frame (or reflections)
Any transparency in your image (this could cause your images to not render)
Same outfit/scene for most photos
Exaggerated/funny faces
Poor lighting, low resolution, or blurry
Extreme angles or cropped faces
Hats, sunglasses, or tinted glasses; big face-obscuring accessories