Obviously there would be plenty of questions, ranging from the most basic (a CD released in 1990 contains 'x' MB of data on it... but there's also the sleeve design, printed track listing etc...) to more complex (how do you measure the data of a painting in computer terms?), but I'm sure if someone were to set about trying to work this out, they could think up (albeit debatable) definitions.
It's actually not all that difficult to measure the data of a painting in computer terms: get a high resolution scan and store it as a JPEG. Of course, this is open to some reasonable disagreements about what constitutes a "high resolution", but the basic principle applies. I'd suspect that it won't make a huge difference, since audio recordings take up roughly an order of magnitude* more space than still images, and video roughly an order of magnitude more information than audio.
* I have no substantiation for this, but it seems about right: a JPEG is a megabyte or 2, while a single movement of a symphony is 10 or 20, and a short movie at reasonably high quality is easily 100 MB.
Obviously there would be plenty of questions, ranging from the most basic (a CD released in 1990 contains 'x' MB of data on it... but there's also the sleeve design, printed track listing etc...) to more complex (how do you measure the data of a painting in computer terms?), but I'm sure if someone were to set about trying to work this out, they could think up (albeit debatable) definitions.