The possible consequences include, but are not limited to, getting takedown notices, Cease and Desist orders, getting sued, and potentially face multi-million dollar fines and jail time.
Just because you don't charge for your app and do not have ads does not mean your game is non-commercial.
US Copyright law lists those non-commercial uses as "criticism, comment, news reporting, teaching, scholarship, or research". Just because it is free and non-advertising does not mean it qualifies as a fair use.
You absolutely need permission for everything you use.