Mockuuups Studio - Fast and easy way to create product mockups on macOS, Windows and Linux.
ResizePixel - Free image editor to crop, resize, flip, rotate and convert images online
Mediamodifier - Create beautiful designs and product mockups in seconds.
Bulk Resize Photos - Resize large photos in bulk
mockDrop - Is a webapp for creating free device mockups including your screenshots.
PQINA Photo Editor - A free, fast, mobile-friendly, online photo editor to quickly edit pictures.