Plagiarism and Scamming are the two things on Steem with 0 tolerance in ant decent community.
There are so many good sites to use and its even possible to do an advanced search on google for photos tagged as free to use. Even if it is free, best to still try and source and say its not yours.
It's pitiful that people enter a community and immediately try to cheat. The fact that you are expecting to earn rewards for work that is not yours makes it even worse. We are upvoting most half-decent content right now, it doesn't have to be earth-shattering.
Give em an inch, they plead ignorance while trying to take a mile, then new account and do it all iver. A pathetic way to earn a living.