Not sure what you mean by unplanned. Obviously, they knew they were making it! So far as the artwork goes, they had a fantastic cover painting done for the album, provisionally titled A Doll's House, until the Group Family released their own Music In A Doll's House, forcing a change.

Several new cover designs were submitted including one of the Beatles' heads carved in rock - in the end artist Richard Hamilton won out, with the plain white. McCartney wanted there to be a blemish on it, and suggested a droplet of apple juice. It was also his idea to put numbers on them, like limited edition artworks.

So, all in all, I think the planning was there. Whether you like the result or not is another matter. I preferred the original painting, which was eventually used anyway, here, as I think it much better suits the mood of the music.