These two articles in American Cinematographer (1 and 2) give some interesting background on the movie; concerning the ship they write:
> When it first appears onscreen, the Event Horizon craft itself resembles a giant crucifix hovering over the surface of Neptune. "The spaceship was built on a cruciform, like all cathedrals are," Anderson explains. "We began the design process by literally scanning [photos of] the Notre-Dame Cathedral into the computer and then constructing the Event Horizon out of those Gothic elements. For example, the big thruster engines are an adaptation of the Notre Dame towers, repositioned on their sides. A lot of the iron and steel work of the superstructure is based on the cathedral's stained-glass windows. The ship also has a lot of triptych windows and big recessed crosses.
> "When Adrian and I first sat down, we said, 'Let's do something completely different,"' says Anderson. "Since we were going into outer space, I felt we had to have a really strong design concept; otherwise Event Horizon would have ended up looking like [a bunch of] other movies cobbled together. We spent a lot of time coming up with a design concept, which we called 'techno-Medieval.' When the lights are on, everything looks very technological and very spaceship-like. But when the lights go off and the haunting begins, you start looking at the shapes, and the architecture is actually very medieval. We extended that techno-Medieval design idea into as many aspects of the picture's look as possible, without rubbing the audience's nose in it."
1: https://theasc.com/articles/unearthly-terrors-event-horizon
2: https://theasc.com/articles/event-horizon-scare-tactics