That's indeed nice of you, but you are reselling their art here and that reselling is simply not okay.

"Free to use" does not mean "Free to resell". It means you can it use as an addition to your own work, but not make it the primary thing to earn your money from.

If you think it's worthy to share a picture, then please just "Disable Rewards" in the settings, then no one will find offense in it.

The Steemit-community does not like to see what you do and it will, sooner or later, result in actions and flags from a lot of people.