I know the feeling; it's always a little intimidating working with someone else's characters. You don't want to make them look ugly, or take too many liberties with their humor, or whatnot. Especially the humor; most jokes come from making fun of someone, but you don't want to piss off the artist.
That being said, I adore this. Both of them are in character and adorable, and Lime is totally going to wear that costume in-comic sometime. It is way too awesome for her not to.