Many (most?) web sites use some sort of icon library such as Font Awesome to create icons of various types. This is a big improvement over the early days when every icon was a separate <img> file. I recommend picking a library of icons as part of MVP. We can then assign certain specifics (perhaps for Search, Users, Menu, etc.) as part of the CSS design specifications/Co-design but in general it will provide a consistent and easy way to add icons in a consistent manner, which is important for a quality user interface.
There are a bunch of different options. My recent experience is all with FontAwesome, so that is what I will suggest but others may have different ideas. Things to consider:
FontAwesome has 2 flavors - Free & Pro. The Free version (which is I think the only one we should consider as Pro would be limiting for anyone else who makes their own Codidact instance) has the actual Icons under CC-BY-4.0 and the code is MIT.
This gets a bit confusing. The original typical FA setup (I think) allowed basically loading anything (within the Free icons) anywhere, anytime. They have changed things to try and monitor stuff (FontAwesome Kit - pageviews, etc.) My understanding is that you can still use it directly thanks the the CC-BY-4.0 license - i.e., if we include the icons & code as part of our package (subject to license compatibility, which is not my expertise) then there would be no monitoring and no issue. That would also be better from a “can anyone put Codidact anywhere” standpoint as well.
FontAwesome is regularly updated and personally I think the quality is fantastic.
Anyone who has serious experience (my experience is relatively limited - primarily on some “internal” limited-use web sites), good or bad, with FontAwesome or alternatives, please comment.