I agree. While I do want to crush anyone's dreams who write such fan fictions, as an older person I would find it inappropriate to write anything sexual or salacious myself regarding the chipmunks. I view them as kids.
I think the best way and most challenging way to write a chipmunk fanfic is to not resort to sexual content to make a story but see if you can write one based on good plot devices and character development.
In terms of artwork its off putting if you write 'Brittany Miller' into Google search looking for a reference picture so you can learn how to draw her and something really shocking comes up. That bothers me.
Each to their own I guess. I commend you for the stamp and you have my support!