It is ok to use it if you change some stuff with it and give them credit, and no (in my opinion ) you could do a paint nod but give credit!!! The reason I am writing this is because I have recently seen one of these posts and not change anything or give credit 3 times by the same guy.
When you dont change anything, its not ok. If you see someone who made this, you should ask them in a friendly tone what they have changed