A professional photographer would not think twice about using a prop when taking a picture.
The idea is that it enhances the subject adding a new element to the picture as a whole.
For the amateur it is worth experimenting as it will widen your knowledge and mean that you will get more out of your camera.
If you have a specific theme or story to tell, then including the right object can make the whole thing more relevant. For example, a picture of a young child can become a Christmas shot simply by giving them a red and white Santa hat to hold. Suddenly you have changed the picture and given it a very special slant and that is what a prop is all about.
It really is a case of getting creative and if you’re out and about with your camera the prop can be an immovable object, like a tree or a piece of sculpture. Sometimes just thinking of something as a prop can make a keen photographer see the potential.
Try not to get carried away as too many other items in a photograph will make it suddenly very busy and the actual subject will become lost. Get inspiration from what the top photographers do, after all they are masters at their craft so we can learn from them.
When taking holiday photographs most of the time the subjects will already have plenty of props, a sun hat, beach wear and a sandcastle. That is why they stand out so easily and explains the advice that you often hear about putting a landscape or relevant building into a frame.