Photos should be well-lit – keep light in front of you, not behind.
Face the camera and avoid sunglasses.
Have high resolution – most modern smartphones can manage this.
Include lots of space around your face (i.e., not a close-up) but you should still be the main subject of the photo.
Length: No more than two paragraphs (paragraphs = 3-5 sentences)
Basic Topics: Experience, qualifications, “focus” or specialty, and perhaps a line about “why you do what you do”.