Creating a new viewmode
As with any other entity in drupal, when it comes to render the rendering it in different contexts, you might want to have specific viewmodes / form modes available.
To create a new viewmode, go to Structure -> Display modes -> View modes -> Add new view mode (or visit the URL:
Select "Media" and then give a name to your new viewmode.
Go back to Structure -> Media bundles, select "Manage display" on your custom bundle, and then make sure you enable the new viewmode in "Custom display settings", at the bottom of the page, and click "Save".