Clear signposting for learners is really important but getting a consistent style to a site or learning unit can be difficult. Google have released 750 icons as a Creative Commons Attribution (CC-BY) resource that provides a large number of formats and sizes. You can download it from https://github.com/google/material-design-icons/releases – this is a big file though, over 50MB.
Although font format is missing from this package, Sergey Kupletsky has created one that you can use if you prefer that approach (most modern professional web sites use this method nowadays).
The combination of all these formats should mean that it is relatively easy to create websites, learning units and even printed material that follows the same design.