After unlocking my bootloader, I got this unattractive warning boot image. I didn't like it, so I replaced it with something I think is more fitting to the phone!
Here's a one:
The download links are your standard logo.bin files. Just replace them through Fastboot.
UPDATE: JUNE 02, 2014
@KidJoe was kind enough to PM'ed me to let me know, there's been a development on customizing Moto X Bootlogos. Please take a look at this post: http://forum.xda-developers.com/showpost.php?p=53098892&postcount=355