MockupsJar
Download free mockups (and premium) on MockupsJar. It is a great website where you can download free and non-copyrighted mockups.
Download free mockups (this is how)
Stap 1:
Go to the website.
Stap 2:
Choose a file you want.
Stap 3 (part1):
Click on the download button.
Stap 3 (part 2):
You can also upload a picture and your mockup will be automatically created.
Demo
Go to this article for more free mockups!
It works really well for me