Few random ideas...
Have retro games in the centre for people to play. Anything from a gorgeous antique chess board to something like Scrabble to Operation! You could put a couple of jars of retro sweets on them too, for the winners.
Have your favourite childhood books (old editions) stacked, perhaps with one or two open at a lovely illustration (Winnie the Pooh, Beatrix Potter & Roald Dahl books would work well). You you put baby's breath on top/next to it to decorate. Old editions of books you like as an adult work well too.
Old family photos in antique frames in clusters, maybe with some fake tea lights in holders like this too https://www.nkuku.com/Item/House_-A..._Candle_Holders/TT28/Tiwi_T-Light_Holder.html
This sounds weird, but a crate of retro drinks, like 50s style glass coke bottles. You could have them empty filled with flowers, or full, in which case they could double as favours.
Have your favours in the centre, stacked up, with a couple of flowers to decorate. Another idea is to make flower wreaths as favours, and bundle them up in the middle, maybe on a large silver platter.
Flowers don't have to take over the tables, you can get bud vases and put tiny flowers in them and they look just as nice. Another thing you can do is to just lay single stems out flat. That can look lovely and relaxed. Or cut the heads off of flowers and place them on a vintage plate/silver platter.
Have food! Cupcakes on a pretty plate, biscuits, sweets. Anything can look amazing if you present it right!
You could also have games for guests, like the one where you stick a name on your forehead without seeing it and have to guess what it is, or games about the bride and groom like quizzes on their pasts. Sounds a bit random but present it in a gorgeous box tied with ribbon and with some baby's breath next to it and it could look amazing!
I hope something there is helpful!
