Facebook Design - Devices - Images and Sketch files of popular devices.
Mockuuups Studio - Fast and easy way to create product mockups on macOS, Windows and Linux.
Smartmockups - Create stunning product mockups, easily and online.
Placeit - Generate realistic product shots in seconds
Mediamodifier - Create beautiful designs and product mockups in seconds.
Marvel (mobile) - Turn sketches into prototypes (new iOS & Android apps)