Rather than looking for background photos on the internet, it's better to build your own library of backgrounds. At least you know what you normally want, so can choose and collect pictures as you go.
Go where? Everywhere! If you don't have a digital camera, use the one on your mobile, these days most have one. I sometimes stop in the middle of a town market to take a few snaps of the pavement, or go up to a building and do a macro close-up of a stone wall. Meadows, fields, sky, beach – backgrounds are everywhere. People sometimes stare, but who cares.
Here is a lichen-covered wall of the 11th Century Bayeux cathedral in France. I was in town having lunch with friends and thought that it would make a good background. So here you are, the wall:
And here it is in the background. To make text stand out better I put it in a Text Box with colour-fill and reduced opacity to 50 percent.