There is a special interface for organizing the images you want to use on the dashboards.
Tabs for the categories you want to assign for your images
Import library - to load saved earlier other library
Add a category
Upload new images to the current Category. You can also drag&drop files from your file explorer
Preview images
Select/Deselect All checkboxes. You can use Ctrl key to toggle individual images
After selection, new options will be offered:
Delete
Move (to another category)
Download as a library for future use