It is possible to add custom image download sizes in the Library Usage Settings. These will then appear for end-users if the selected asset fulfills the necessary width requirements.
To set this up, click on the settings cogwheel in the side navigation. Then click on "usage settings". Here you will find a section called ‘Add Download Image Size’. There, you’re able to predefine available download sizes for your assets which will ultimately be shown in the consumer view of your Media Library.
Note that the width has to be documented in pixels. Once you’ve predefined various export formats, your brand consumers can simply export assets in the right format by choosing the respective download size.
In the consumer view on the library front-end, users can hover over the dimensions to learn more about the resolution (dpi) to avoid print quality loss. In the example below, anything larger than 16.26 x 10.84 cm would start resulting in a worse quality for print products.