E-mailing of photos is preferred. Quality drawings are the result of quality photos! The mutual objective is the "WOW" factor. We both want to capture the subject's expression & personality.
Outdoor daytime lighting is usually better than indoor lighting. Full shade is best. Sunlight creates shadows. If indoors is the only option try to use light streaming in from the outdoors.
Photos taken with a flash are NOT good for reference. Flash tends to blow out the details plus it causes red eye or worse.
Photos need to be sharp with good resolution. Low resolution, pixelated or badly compressed digital images are difficult to work from. When they are enlarged they become grainy and blurred.
I can improve some photos but an excellent photo to begin with is always preferable.
Please allow enough time, especially if it's a surprise gift and/or for a specific date.