Try the new Art Tatum disc from Zenph, "Piano Starts Here." The second half of the disc is binaural - that will give you a great demonstration of your headphones' capabilities.
Also try any music that was recorded live, with an audience. You'll find much more of this with classical or jazz, but you'll find some for any genre. Rhose will demonstrate soundstage better than studio recorded music where an engineer separates the channels.
To more directly answer your question, I agree with Uncle Erik about "live" performance recordings where an audience is involved. It depends greatly on the actual sound stage capabilities of various headphones. With some everything is "in your head" while others have a sonic presentation that seems to extend outside of one's head.
For what exactly about the sound stage are you testing? I hope you're not attempting to measure the exact size of your headphone's sound stage. You will drive yourself "crazy" trying to determine that.
Read the first post of this (now closed) thread:
I would not recommend tracks that have fantastic soundstage on their own (especially not binaural), as these make any decent headphone sound great. A much better test is what they can add to fairly mundane recordings.
a little bit off topic but i gave Unplugged a listen and OMG i can't believe I haven't listened to this before. And its exactly what I've been looking for in music for a WHILE now, also i downloaded and installes ASIO4ALL its made quite a difference. didnt really expect that. all i can say is thank you all for that suggestion, it really highlights the soundstage too!
btw any other Eric Clapton albums that are good? or something in the same vein?