A brand icon for the macro placeholder. For best results, provide a square image that's at least 80x80 pixels.
Optionally, you can provide an image placeholder to represent what the content will look like in the editor (if you don't provide one, your brand icon is shown).
How do users edit your macro's properties?
When a user adds your macro to the page, or edits a page with the macro already added, they'll click the macro placeholder (shown in the image below) to see the macro properties panel. They can also double-click the macro placeholder to bypass the macro properties panel and go straight to the macro properties dialog.
UI components
Macro properties panel
Macro properties dialog
Recommendation
Provide quick actions for editing your macro's content in the macro properties panel. This is for editing commonly-used macro parameters, like iframe size, deleting the content, and a button to go to the macro properties dialog for more involved editing and previewing the content.
Use the macro properties dialog for more involved or comprehensive editing of macro content. Some examples are entering a data source or URL, and filtering and sorting options.