Before James Joyce's "Finnegans Wake" was published, it was called "Work in Progress" for many years. A number of literary critics once published a collection of essays about the still-unfinished book, called, as I recall, "Our Exagmination Round His Factification for Incamination of Work in Progress." That's a good round Latinate phrase, though I admit it's a tad unwieldy for a sign on the door.
Or, you might try "Imperfectus": literally, "unfinished". That sounds like it might resonate with your thought. (Of course, my most recent Latin course was in 1967 at Central High School in Philadelphia, so don't consider me the last word by any means.)

Aloha (alohae, alohas, aloham, aloha),
Mark