Undraw
Undraw offers a wide range of free open source illustrations by Katerina Limpitsouni
Stock Assets
Pexels
Pexels is a stock photography site. The pictures are free for personal and even for commercial use. You can modify, copy and distribute the photos. All without asking for permission or setting a link to the source. So, attribution is not required. All contents are released under Creative Commons CC0 (Public Domain).
Unsplash
Unsplash (https://unsplash.com/) offers free “do whatever you want” high-resolution photos with no attribution. They have their own “Unsplash” license that essentially says you can do whatever you want, so long as you do not try to sell them via a similar service. If you are using Unsplash for mockups, check out Lorem Picsum (https://picsum.photos/). It …
Pixabay
Pixabay is a free stock photography site that offers free images and videos you can use anywhere. Made up of community of creatives, sharing copyright free images and videos, all contents are released under Creative Commons CC0 (Public Domain), which makes them safe to use without attribution (asking for permission or giving credit to the …