All our schemas use icons that are displayed in the studio. We use Material icons.
In this reference article, we've put together some of the icons available, plus their name that you need to use in the schema. There are lots more icons available. To see the full range available, open the studio, click Components, select an existing component, then click the Edit icon button on the overlay. There you can search all the available icons and get the required name.
You can change the icons of your components in the studio, but you'll also need to edit your schema, so changes aren't overridden.
List of icons
Some available icons with their schema naming are listed below: