Blocks should have descriptive icons

It would be a huge improvement if blocks had descriptive icons that illustrated what they did. This is especially true when the tool is used to teach younger students for whom reading words like "rotate" is not quite second nature.

I could work on making these as images; but I've also just switched over the UI icons on the main site to https://materialdesignicons.com/ which has a lot of icons in SVG format that might be useful?