You certainly can remove or edit photos that have been contributed to your frame.
First, you need to locate the photos that have been contributed to your Aura Frame. To do this open the Aura App and click the "Settings" icon on the top right. Next, tap your frame name and under Family Share click on the person whose photos you would like to remove or edit. Here you will see all the photos that have been selected for your frame by that particular contributor.
To remove a photo entirely from your Aura Frame simply uncheck the photo. When the check disappears the photo will be removed from your Selected photos.
To edit a photo, tap the photo to view the details page and click the bottom left icon (three small dots) where you'll see three options; Display Now, Reposition and Share. Option 1, "Display Now" allows you to send that photo directly to the frame. Option 2, "Reposition" allows you to crop or zoom the photo. Option 3, "Share" allows you to download and send the photo to someone else or simply save the photo to your own photo library.