Ever notice those FBI warnings in the porn credits?
You should.
Now, likelihood of being sued. Look at it this way. A studio has to hire an attorney and that attorney has options (most likely the studio already has attorneys on retainer anyway). If you are lucky, you get a Cease and Densest letter; they file a complaint with the local FBI office and an agent knocks on your door; worst they try and squeeze blood from a turnip and make an example out of you-- copyright, damages to their business or brand, unlawful uses of images etc...
Do you have enemies that would gladly rat you out to the studios you are getting your material from? LOL!