This only works with Devhook, but if you replace certain files in the dh folder you can change XMB for any firmware version you are running on devhook. I basically took a new gameboot, bootsound, font, and backgrounds for 2.71.
Here's a link to where i found this out:
[PLESE DON'T ADVERTISE OTHER SITES. REPEAT VIOLATIONS WILL BE BANNED -HD] (sorry didn't know, it just isn't my own and i wanted to give credit)
And some screenshots: