Lyric discussion by ICantUnderStandYou 

Cover art for Decorate The Spine lyrics by Knapsack

I'm not 100% but I think the song might be about how the singer isn't perfect or he's broken but he's met somebody he really loves and is willing to do anything to make the relationship work, 'But I'll decorate the spine for her' meaning he'll act interesting or like he's got it going on to please her. Like I said, I'm not 100% on this.