I have never pulled it down and I don't believe its labeled as a changing table but (some of?) the 737 lavs -- at least the F LAV -- do have a fold down horizontal surface.

My brain says it would be a bit small to change a baby on -- but I don't know what else it would be there for...perhaps I'm just blissfully naive. Narrow body lavs are tight enough with one human adult... Good luck maneuvering a tiny human, full human, and table!