Like I said, sheet music. Nothing very complex; things like the score images in the Old Scottish Flute Music part of my website. They can be presented as JPGs, GIFs or PDFs, whichever the device is happiest with. The sort of use I might have is for the tunes our klezmer group plays - about 200 pages of A4, currently in a heavy plastic-pocket folder. They will all be black and white.

But that's too big for a Kindle and a bit too many for a flip-through-one-at-a-time control interface.

Typical flea market prices for a digital picture frame are about a tenth of those for a small laptop. And a laptop is the wrong shape to support on a music stand in a normal playing position. An iPad would be ideal but I can't afford one.