I got into a long debate with the resident HM experts (you might have been part of it) when the queue first was added about the tone and when the ghosts should be revealed. It was informative, but neither side budged...nothing has changed.
17th & 18th century family oil portraits associated with genre have a particular realism. If the attraction were design to be a more realistic, dreadful, gothic horror experience from the Foyer on, you might see portraits that emulate this style.
Instead, the Haunted Mansion paintings eschew such realism (or maybe mix it in at random, i.e., hanging corpse) and are much more whimsical & toonish in the Marc Davis-style, setting a precedent early in the experience: