A picture says a thousand words. More relevant for this context is that a picture just adds visual appeal to the blog/site.
Here are a couple blogs that list several sites where one can obtain royalty-free images.
- http://www.lifehack.org/573898/10-best-sites-that-offer-gorgeous-free-images-for-blogs
- https://blog.snappa.com/free-stock-photos/
Personally, I’ve been using Pixabay almost exclusively. It has a pretty good selection of photos. I’ll keep using it ’til I find it harder to find good images. I’m not a fan of hunting around to multiple sites to find the perfect image. Good is good enough for this purpose.