You can find good quality pictures and videos here:
Hope it is helpful.
Why do you need free ones? In my experience the free ones are seldom any good. Most of the good stock photo sites allow you to download watermarked proofs. As a photographer free work is killing the industry. When you need good photos there won't be anyone left to help you.
I highly recommend you to use :https://www.shutterstock.com/
It has monthly 10 image free for one year .If you sign up with the instructions .
I think it must be some of the referral code as i have already used and i got ten image free for one year monthly .
Please let me know.
Recently I came across a great article on Templatemoster. I am pretty sure it will be useful for you, check this article, it will help to find all the answers to your questions - https://www.templatemonster.com/blog/watercolor-freebies/
Here is the list of the resources with free HD pictures: