It is okay it use publicly, but only if you pay the license fee through Getty Images - this requires setting up an account and buying credits that you can spend on licensing the images (which you can then use royalty free without the watermark)

Lots of good royalty-free images that don't cost any license fee can be found here: https://unsplash.com/

If you can't find what you're looking for at unsplash, check these other sites (although some require attribution):
https://blog.snappa.com/free-stock-photos/