A little story I have to tell you about.
Few months ago I discovered that someone stoll 3 of my illustrations to make an ad for a website he was working for. I decided immediatly to hire a lawyer.
Few months later I won a lot of money thanks to this.
So, to be clear, you CAN'T use my art for your own benefits, they're protected by copyright laws.
But if you do it anyway and I know about it, be sure I'll sue you and you'll have to give me a lot of money