Ask people why they have not put a photo up and you will get one of two answers. Either there are no decent recent ones, or, more often here, they would rather not be recognised. Both are fair, and the second one is a real consideration in a country this size.
The trouble is that a profile with no photo gets very little attention, and you will know that yourself from scrolling past them. So it is worth solving rather than avoiding. Five things, and the first is the one that matters most.
Smile, and mean it. Smiling photos get about twice the messages. The difficulty is that most of us have exactly one camera face, learned for passports, and it says get on with it. Hold a smile deliberately for four seconds and it turns into a grimace, which is why so many perfectly good photos look pained. The trick is timing. Get whoever has the phone to say something daft, and take the shot in the second after you laugh rather than during. That is the one that looks like yourself.
Light does nearly all of it, and the light you want is free. Sit facing a window in daylight and it comes at you soft and even from the front, which flatters everybody. What ruins a photo is the bulb overhead at ten at night, which drops shadows straight into your eyes, and the bathroom mirror, which has never once helped. Outdoors, morning or late afternoon beats the middle of the day. Anywhere pleasant works and doubles as something to be asked about: the garden, the beach, a headland, the seafront on a bright day. And here is where the privacy point matters. Have a look at what is behind you before you post it, because a distinctive gate or a shop name will tell somebody more about where you live than you meant to.
Two mechanical things. Put yourself in the middle of the frame, because dating sites crop pictures automatically to fit different parts of the page and they always take it off the edges, so anybody standing to one side loses an ear. Head and shoulders, or head to waist, with a bit of room around you. Then get the camera up: hold the phone a little above eye level and look up at it slightly. Taken from below, everybody acquires a chin they do not have in life. The grandchildren have known this for years.
Your best photo is almost certainly one with four other people in it at a wedding, because that is when your face is doing something honest. Use it, but further down the gallery. A stranger should not have to work out which one you are, and "sorry, are you the one on the left?" is a poor start. Leave out anything with an ex in it, and with a late husband or wife too. Not to pretend your life did not happen, but because a photograph carries none of the story, and you would far rather tell that yourself, in your own time.
More properly taken photos turn up on the site than used to, and they do look well. They are not always as dear as people assume either, particularly with somebody working from home rather than a studio in town. One member found a better way around it altogether. He told his son the family had not had a decent photo taken since a christening and it was a disgrace. The family got their portraits, he got a headshot, and somebody else got the bill. If that is not on, ask a grandchild. They have been photographing themselves since they could hold a phone and will take great pleasure in telling you what you are doing wrong.