question about copyright and other..

hello,
im newbie in the adult business, starting one porn-blog with amateur or amateur-look pictures, videos, blogs..
because i havent too much , then these photos videos downloading from arund the net WITHOUT(!!) a watermark. (next step i put here my own watermark )

so..

what happening, when email me one producer: THATS MY SET FUCK YOU DELETE THESE PICTURES!! I GO TO THE POLICE!!
i need these pictures delete?

or email me one girl-men: IM ON THIS PHOTOS YOU BASTARD I GO TO THE POLICE !!

what i can make to avoid these troubles?

sry for english