GPLDL - 1066 GPL-licensed WordPress themes & plugins for free
Mockups Design - Mockups Design is the most leading web-based application that comes with a vast collection of creatively design mockups for all kinds of products and devices.
LyrWP - WordPress themes / plugins / services curated.
Anthony Boyd Graphics - Anthony Boyd Graphics is the fastest-growing platform that offers high-quality and advanced level mockups, textures, 3D models, and UI kits for free to help designers to save time and effort.
Blocksy - A lightningfast, innovative and supercharged WordPress theme
Mockuuups Studio - Fast and easy way to create product mockups on macOS, Windows and Linux.