Every time you download an image that design is saved in the "Saved Designs" section. This can be accessed by clicking the "disk icon" which is located at the bottom of the left menu.
Over time the "All Saved Designs" area can fill up quickly.
By clicking the "Project Designs" tab you can filter just the designs that are associated with a specific project.
You will always notice that each image is marked with the date that it was saved in place of the category information.
If you make any updates to a Saved Design it will automatically be "bumped" to the top of the list for easy access.