I would suspect a Template with eBay sanctioned code would be usable. I just don't know how radical the changes will be to use of elements like background, etc. It's possible they won't be allow as a detraction from their view of "Buyer Experience", which seems to be the excuse for any unethical conduct they want to justify. If your music play method meets their list of eventual methods, it will be allowed. Flash Players won't be allowed, but that's not what you're doing. I honesty suspect there will be changes coming that may make some 3rd party features less attractive or unusable. I believe eBay is looking for any means to add to their bottom line, including take-back of territory granted to the 3rd parties. However, if eBay is truely going to RETAIL MODEL 100%, then small-business and the 3rd parties might have no venue for operation anyway. The surviving Power Sellers and big corporations will tow the eBay line, using pure eBay services in big fat packaged discounts (already being discussed and granted).
I know Auctiva is at Live! Chicago. The reports I'm getting are almost shocking: low attendance, empty booths, no registration line, and near fist fights and shouting matches over the policy changes. YouTube has some interesing video broadcasts on the subject. I'm not there and happy to not be there.
As I said....I'm on break while the insanity continues to mount. I did get a great BD present for my 5 yo grandson on eBay, just a few weeks ago. He loves McDonalds and Jurassic Park. It's what made eBay great; that rare thing you could only find on eBay. Sad, that era is coming to an end. Here's what I found....
McDonald's 1993 Employee Jurassic Park Cap
Tell me your going to find THAT at BUY.COM.