The animals in formaldehyde are cool, the sliced cow and calf having more impact than the more famous sharks.
The painted dot pieces are also quite cool, and I understand their impact now, something that I didn't get before. The larger pieces are too large to take in and I was more taken with some of the medium pieces. I could happily look at them trying to look for a pattern, that I know isn't there. Stare hard enough and a sailbarge appears.
One tip I would give is to do the rooms in order. There's a queue for the butterfly room, which won't have the same impact if you return to it as we did. (spoiler - there are better butterfly pieces in later rooms)