Digital Usage Rights
Google image search is ok if you find an image that gives you appropriate usage rights (ref: https://creativecommons.org/licenses/)
You need non attribution commercial use, don't be tempted to use any image.
For all images supplied by clients it is their duty to ensure that the correct usage rights apply.
Some clients have been caught with $4,000 bills from Getty Image lawyers
If you are looking for free some sites are:
At YPO we use various paid services from Getty Images (istock) and other services.
Let us know if you want us to find or whether you have found what you like.