Images won't display if I point my default app folder to a non appsheet generated folder

I have an app that needs to show images from a folder that isn’t one of my appsheet generated folders. Whenever I set my default app folder to the folder that appsheet generated for my app it works, but if I copy and paste my image into another folder, change the default app folder I get no images. I don’t know why this doesn’t work. Any one know?