Hi, Paukstis. Sorry to be the one to break this to you, but you cannot freely use images nor soundtracks found online. Same with assets from games - even if you bought them.
The fact of the matter is - buying a game allows you to play it. And that's about it. Your mileage may vary - it depends on your country's copyrights. In EU it's strictly forbidden, and in fact - punishable by law. You can be charged for hundreds of Euros for copyright infringement. Really. It works that way even if you're "not for profit" or doing it "just as a school project". There's a chance that your country has something like "fair use" (which allows you to e.g. quote something, and in some cases - even lend a book or a movie to your closest friends and family). Funny thing is - games are considered "computer programs", which are not subject to fair use at all, at least where I'm from.
Good luck. And just to be safe - better stay clear of potential copyright infringements!