To avoid copyright problems and get good quality images use a stock photography website. I use 123rf.com . There are two options for purchase, credits or subscription. Credits start at $15 for 5 xxl images. Subscription cost $89 for one month which allows 5 downloads per day for a total of 150 images.
The second option, which is FREE, use Flickr.com. To find images that are not copyrighted just enter the type of image your looking for with the words royalty free with it or copy right free. You'll see only the images that are free to use any way you like. The quality will not be as high but you'll find something you can use.
Note: always read the use agreement with any image on 123rf, and flickr.