This post is ancient but the question is still relevant.
For a few years, I've been regularly using the TwistedWave app on my iPad. A year or so ago, an update included a new MP3 tagging menu. Title/Artist/Album/Year/Track#/Track Count... And you can embed photos from your Photos app! Very cool!
I have been wishing that Goodreader would include support for reading MP3 tags. I use that app a lot and seeing the details and embedded artwork would be a nice upgrade. I got into a podcasting thing recently so seeing these this has become more important for checking various files.