This was one of my favorites. I watched it with a dear dear friend.
The Title, the Painted Veil may refer to the wedding veil a symbol of purity, only this veil is painted, or fake. It is a reference to Percy Bysshe Shelley's 1824 sonnet, which begins, "Lift not the painted veil which those who live, Call Life"
This couple move from living that masked, veiled life to a sharp reality and this give rise to the by line to the title, which I absolutely love, "Sometimes the Greatest Journey is the Distance between Two People."
That byline is from W. Somerset Maugham Novel from which the film is adapted.
Great moving movie.