As of WordPress 4.3, you can set the “Featured Image”, “Set featured image”, “Remove featured image” and “Use as featured image” labels to whatever custom text you’d like to use instead. You can do this when the post type is registered using register_post_type().
Here’s an example of how to to it:
Further documentation is here: https://developer.wordpress.org/reference/functions/register_post_type/
WordPress < 4.3
For sites running a version of WordPress lower than 4.3, here’s how to change/filter the featured image metabox title and link text in WordPress:
To use this code, just make these changes:
- Change “my_post_type_name” to the name of the post type for which you want to change the featured image text.
- Change “NEW TITLE TEXT”, “NEW SET TEXT HERE” and “NEW REMOVE TEXT HERE” to the new text you want to use.
- Change “km” to the function prefix & text domain of your choice.
Note: The default “Remove featured image” text is still visible immediately after an image is selected. The code above does not address that.