Yeah, I got the perfect solution for you: if you want free art, make it yourself.
Or use stock pictures. Either that, or pay an artist for their time and work. I'm sure there will be plenty of great artists willing to work on your project for a fair rate. I say this without any rudeness meant at all - don't ask for free art! Artists need to eat and pay their bills. Asking for free art disrespects the time and work it takes to make it, and contributes to devaluing the profession in general.