Restore from backup restores all of your preferences. Since the Emoji icons were just a preference edit, it kept that edit. Also, if you use a jailbreak to turn your battery into numbers, it will keep that too!
Every time I jailbreak, I get annoyed at how slow my phone goes so I end up un-jailbreaking anyway. I guess from time to time, I try it to see if it's made any real progress... never does.
Sometimes those plist edits are fun though.