It would be great if you could either shuffle the existing collection on an iOS device by albums (so when one album finishes a different one starts playing, same deal as track shuffle but at an album level).
There are a few ways I've seen this implemented in various players; Foobar (Windows Desktop) does it exactly as I described above. An iOS player that I used before VOX would present a grid of randomly four-six albums (this would depend on your device, four titles for >= iPhone 4S, 6 titles for <= iPhone 5); the user would then tap on an album cover for it to start playing. Both have their own advantages, - perhaps for the iOS on-the-go format the former would be a better alternative, but I do like the ability to pick from a bunch of random titles too.
For people with huge collections, especially Loop users, this would be a great chance to revisit some forgotten favourites; for people in an undecided mood, - a chance to 'go with the flow', - and so on and so forth.