Do you need a image to display a message or quote, why not just use text and decorate the label differently if you need to.
This way you can upload a csv type file list to the app, containing all the quotes/messages, and call a different index from the list each day
If it has to be an image, then it may be better to store all of these on a web file server, and call them in to the app as required
(or download them all, file by file, on the first run of the app)