Interesting… they used to be in the widget, but the updated UI omits them. 

Icon is a square. My design template is 448x448 pixels. I typically double the recommended minimum size, so I’d say they recommend 224x224. 

I don’t use the full image as often, but it looks like I have a template for 1440x544 pixels. Not sure if that’s doubled or the minimum. 

The widget is called Quick Links and it has different card styles you can pick from.

If you need more control, however, I have made a custom html widget work for longer rectangular widgets with mouse over.

We have a lot of guidance around design elements in this article, which links to Figma:

Here’s an example of the guidance for Quick Links from there: