1- Flaticon
Flaticon offers a huge library of free icons and stickers in a wide variety of formats including PNG, SVG, EPS, PSD, and BASE64. However, icons are provided for free only in PNG format, for other formats you need to have a premium subscription.
2- Iconscout
Iconscout offers a growing library of design assets that include vector icons, illustrations, 3D assets, and Lottie animations. While the majority of these design resources are only available for premium subscribers, you can still find tons of free icons, illustrations, 3D designs, and Lottie.
3- UXWing
UXWING is another great website that provides free clipart icons that you can use in your multimedia projects. Icons can be used for both personal and commercial projects without any attribution (read more about UXWing licenses here).
4- Icons8
Icons8 offers tons of free professionally designed clipart icons, vector illustrations, photos, music and design tools. A free plan on Icons8 allows you limited access to the site’s resources and you are also required to add attribution links each time you use an asset from the site (learn more about Icons8 free license here).
5- The Noun Project
The Noun Project offers more than 3 million icons available for free in both PNG and SVG formats. Photos from the Noun Project are licensed under Creative Common License (CC BY-NC-ND 2.0) which means that you can use them for non commercial purposes provided you add attribution to the source.