Cover images that are displayed in augmented reality are downloaded by the mobile application after the target is recognized.

This is why it is important not to upload cover images of too large size and weight. This is even less relevant since cover images are usually displayed in small dimensions, for example at the size of a button or a logo. If a cover image is too large it will take longer to show in the app. We recommend using cover images ranging from 10KB (logos) to 100KB.

Tip to lighten your images : https://tinypng.com/