Perhaps think of the pond/lake the swans are a-swimming on and do up some nice pond - edge flora. You could even have a cute arched footbridge to an island sub -theme.

Think of the swans as a starting point. You can draft a whole little world with the swans as a focal point.

Don't be literal. Take all of it as a riff on the day of a swan or lifestyle of a swan or the day you happened to see swans. Maybe even have a black swan hiding among the edges.

A circular mirror as a lake with the seven swans swimming on it, with the rim of the mirror trimmed with evergreens and ribbons to look like a wreath.

A Victorian-style carousel with swans. Some instructions here.

I don't understand the parameters. Is there a budget? Does it have to fit in with anything other than the theme, like does it need to be Victorian or is it that just where it is?
Seems like there are way more options than maids a milking or drummers drumming.

My first thought was incorporating them in a way so one had to find all seven, then to something balletic. It seems like it could be pretty simple to rig something where seven "swans" "swim" when people enter the room, either with strings or projections, etc. It's quite endless depending on what you have to work with.

There would be a lot of possibilities if bandwidth and money were no object, but assume a shoestring to nothing. Yes, it has to be Victorian, at least plausibly so. And it needs to be much simpler than an art installation type thing - basically, decorate the room so people can ooh and aah as they move through without stopping. Nothing interactive.And there will be a constant flow of people.

At this pond on the Miami of Ohio campus, there used to be this sign that warned: BEWARE. MATING SEASON. Apparently swans are vicious during mating season.

Don't know how that helps with decorations, though.

Swans are vicious creatures, but that's neither here nor there.

My first thought was zoetrope, but rather inside out, projecting on the walls-- but turning away from the creepy Victorian spiritualists stuff at hand, I think a quick, cheap option for dramatic impact would be some combination of wall treatment and rotating shadow lamp: either reflective swans poses on the walls that catch the light of a dramatic moving shadow design or dramatic swan pose cut outs moving on an intricate reflective wall design.

Light catching stuff is cheap and easy, from rolls of iridescent cellophane to mirror spray paint. The rotating lamp part can be made from a the heat of a lightbulb or any used motor, like from a music box or a baby mobile. Even new, rotating lamps are only around $10 maybe? So the only real hardship is picking and cutting out designs. Some Muybridge type swans sequentially rearing up or extending wings with, say, snowflake patterns or a copse of saplings or a Victorian wall paper design, etc.

Anyway, that's kind of the maximum bang for your buck idea off the top of my head without knowing anything else. Depending on the choice of materials, it's something that could have been done in Victorian times and, depending on the choice of designs, can be very striking and elegant. Simple that down and you can just have a rotating lamp of swans, which might still be more than what's expected.