I love the added depth and contrast that the small lines of writing add to the green paper with the large, swirl-style holly leaves. Myself, I would consider writing the lyrics on all the letters and finishing them all with Mod Podge or satin Royal Coat. Then you could add ribbon or hardware to the top left and/or bottom right of the word to give the eyes a place to start and/or finish. There's not a lot of imagery in the song Joy to the World that is easy to incorporate (a crown? a horn?) but I don't know -- a sprig of holly on top of the J or on the left side under the cross-stroke? A cluster of bells somewhere along the right side of the Y?
If you have an idea of where your mother might display the word, try setting your letters in a similar location to confirm that you like the results when they are set against the scale of objects they will be displayed against.
I'm no artist or designer tho; please upload the finished project when you're done so we can all be inspired by you!
