Screenshots must depict the actual content of the package in some way, and not be misleading.
Do not use idealized mockups or blender concept renders if they do not accurately reflect in-game appearance.
Content in screenshots that is prominently displayed or "focal" should be either present in, or interact with, the package in some way. These can include things in other packages if they have a dependency relationship (either way), or if the submitted package in some way enhances, extends, or alters that content.
Unrelated package content can be allowed to show what the package content will look like in a typical/realistic game scene, but should be "in the background" only as far as possible.
From https://content.minetest.net/policy_and_guidance/#7-screenshots :