Looks like I missed this thread, as activity had died down back in 2002 before I joined Yestalk!
My personal favorite is Tales, as far as the outer packaging goes.
If you're talking the package as a whole, then Tales is still excellent, but you also have to give nods to Yessongs, for its four paintings and the interior booklet, and CTTE for the interior painting and those calligraphic lyrics . . . how often I listened while perusing those!
And Relayer is so wonderful too . . . the detail is just gorgeous . . .
All the Dean stuff amazes me . . . I remember purchasing Views back in the 70's when it wasn't available except by import, and I finally found a bookstore willing to import it for me . . . sat mesmerized at all those beautiful images all in one place . . .