Since the gallery and board database views have “preview” options to display the cover image, and the app has the option to display the cover image. It would be nice to have the option to update your cover image from the mobile app. 
Btw, this project is amazing.
Greetings, welcome to the NotionApps family.
Hi Shannon — glad you’re here, and thank you.
The cover shown in the gallery, on the board, and in an image component is the picture already set on the Notion page. The app displays that picture. Changing it stays in Notion, so the page remains the source of the image.
If someone needs to change a picture from the phone, add an image or file property to the database and put that field on an update form. That change is saved back to Notion.