I've got a 7" (diagonal) frame that was given as a present. The resolution is only 432x234 pixels -- not very good for music notation! I think you can get better resolution than that, and bigger screens up to 15"; the price is quite high though. And you have to keep pressing a button to get the next image. You might do better to go the whole hog & get a tablet.

Or you could carry on using paper sheet music!