Please go to about phone and confirm the base band version. eg.30 is sprint. If that is .29 than it worked as it should but the bg image did not go back to the boost one. If anyone can upload the picture you can just make that your bg and all is well.
I am probably mistaken but the stock image for my phone was on the memory card and through all my flashing and even using cwm it never kept that default image for whatever reason. It just used the first wallpaper option that was not in the gallery. (it did keep the picture from my later made backups but the factory image never stayed for whatever reason)