To create multiple cards with different backgrounds at once:
Click the three horizontal dots icon on the bottom center of your screen (1) and select 'Image upload” (2)
Drag and drop your images from your finder window to the left side of the editor
Note: With the multiple-image upload functionality, images are automatically set as backgrounds for new cards. New cards are named after the image’s file name, but you can always rename them by logging in as an admin. To speed things up, we suggest that you rename your image files before upload.