Flaticon - A database of free vector icons.
Mediamodifier - Create beautiful designs and product mockups in seconds.
Font Awesome - Font Awesome makes it easy to add vector icons and social logos to your website. And version 5 is redesigned and built from the ground up!
Mockuuups Studio - Fast and easy way to create product mockups on macOS, Windows and Linux.
IconArchive - Search through more than 735,000 free icons. Browse icons by category, artist, popularity, date. Organize and share your favorites.
Placeit - Generate realistic product shots in seconds