Using images found through a Google Image Search may be illegal. Most images are copyrighted by default and usage generally requires permission – especially for commercial use.
Google does now offer the option of filtering images by usage rights in your search. The screenshot below shows an unfiltered search. Click on the ‘Visit page’ button (see red arrow in screenshot below) to go to where the image appears online in order to ask permission to reuse the image or inquire about where they purchased their licensing.
You can go to ‘Search Tools’ and then select ‘labelled for reuse’ from the pull-down menu to search for images to use for your business that are not licensed. Not sure how, but apparently Google is able to identify the permissions associated with an image.
A word of caution however! Despite the filtering for creative commons rights in Google Image Search, many of the images that you will find through the service have been used illegally and may put you at risk for copyright infringement.
Ethically, I prefer to either create my own graphics or to purchase the license to use another artist’s work.