I also believe the ride evolved over time. The ride as it was in the 90s and the ride as it was in say the 50s/60s are two different things - as props broke/got replaced. I don't know anything about Bill Tracey - however because of your post I took a look at a few websites dealing with his work - conceptually I could see a visual relationship (i.e style) that is compatible with the Viking and the Dragon that were on the outside of the ride.
The owners of this park cared very little for its history. They owned this and a slew of night clubs (Narcissus/Lipstick in Boston for example) and saw it as a business only.
The shift from an exclusively family oreinted park to one featuring bands and cover bands such as Steppanwolf, Max Creek, Gloria Estefan, Level42, The Machine, Dread Zeppelin, Snap, Kenny Loggins, and others reflects the influence of owners with nightclub backgrounds.
In short, history preservation was not of paramount importance to them - they would not have broken up the carousel if it had been.
Park employees painted some of the stuff inside. Primarily the cars and the tombstones in the cemetary scene. The castle on the back wall of this room was there for as long as I could remember. When you passed through this room there was a little bit of strobe lighting effect (in another picture you can see one of the lights still remaining).
There was also blacklighting in variuos room in the house of horrors so that any white clothing you might be wearing would glow.
Someone else once said to me that some of the props were done by RISDE students - but that info is suspect. I had the impression they were speculating rather than approaching it with true knowledge.