Neil Gaiman, upon becoming good friends with Tori Amos, modeled Delerium after her. Tori can be found singing about the author of The Sandman comics in her song "Horses" from Boys for Pele:

...and if there is a way to find you i will find you
but will you find me if Neil
makes me a tree...

Neil soon made the tree for her:

That happened in a new bookseries by Neil Gaiman and Charles Vess called Stardust. The first part of this 4-part series came out in October 1997. The Tori tree appears in issue #3 that came out in early 1998 in a special illustrated version.

- thedent.com


Interesting side note:
At first I thought that she was saying "Neil makes me a dream", but I read the lyrics and got really disappointed as I started to node this. I did some more research, specifically at thedent.com and found a reference to this lyric. I felt redeemed :). Major props to the page... it has LOTS of tori & gaiman info.