This might seem really obvious but your LinkedIn profile photo should be a photo of you. Only you. Not your spouse. Not your child. Just you.
LinkedIn is not the place for family portraits. Those go on Facebook.
I am always surprised by seemingly bright people who have great experience, a strong education and relatively high profile jobs and yet their LinkedIn image is them with their dog. It begs the question: who is running the show? You or Mr. Snuggles?
I suppose if you were a vet, it might be okay to have you pose with a “client” but I’m not sure I would advise a criminal lawyer to do the same. Similarly, it would be okay for a chef to have a ham or wheel of cheese but if you are banker, leave out the stacks of money.
The other issue with putting job elements into your image is that you will always be associated with that role and if you are looking to make a change, it will be more of a challenge.
The best thing is to use a simple, well-lit shot of you from the shoulders up looking reasonably professional.
Your LinkedIn profile is the gateway to millions of people. Make it count.