Hi Barry. Pictures on the internet are not free to use. Most of them are covered by copyright. The exception are those placed into Creative Commons by the copyright holder, or those marked 'Public Domain' by the government authority with the copyright ownership. Or something where copyright has expired (70 years after the photographer died).

The fact that people also use the term 'public domain' to describe anything online does not mean anything online is free to use.

I've got a whole section on Copyright law, and it's a murky area, but the bottom line is unless you know otherwise, assume all material is copyrighted and cannot be used without written permission from the person who owns the copyright (usually the photographer). This is what happens when you hope for the best. https://medium.com/life-tips/i-got-a-1000-demand-for-using-an-image-off-the-internet-8c7d236126cf