Any photo I take, any artwork I make, or any sentence I write belongs to me. Copyright automatically belongs to me the creator even I have not added any C’s in circles or legal jargon. That is how copyright works. If you want to borrow (and then return) or use anything I make, just ask. Don’t steal! Yes, it is stealing and you would be held liable.
A friend wrote about her misadventures with somebody stealing her images for commercial purposes. I have heard about people stealing entire websites and inserting their names here and there. Is it really that hard to make your own? Or to hire a kid in high school to do it for you? Do the right thing, people!