Yes. You can add an icon as an image - you just have to get the icon in an image format! For the icons that are available to use with Quick Links, start with this amazing site that allows you to find and export any of the fluid icons: https://www.flicon.io/ Use the ability to export the icon in any color you want so that it matches the theme of your site. Then add the icon as an image in the image web part. You can do the same thing with the icons in PPT by adding one to a PowerPint page and saving it as a picture. It's multiple steps, but it can be done!