Hit up yardsales and buy mismatched tea cups – put votives in them as centerpieces and set them at different levels using old books, or boxes wrapped in vintage-y fabric…
Not sure how many people you’re inviting, but set up a few different tables, covered with old table cloths/pretty fabric). Buy cheap mosquito netting and hang over the tables to create the effect of having tea under a tent in the garden. Preferably do it outside or even in a room with lots of windows looking out onto a yard. Have lots of light, lights of pale colors. Make paper flowers out of old book pages, or vintage looking paper.
Finger sandwiches, petits fours, pastries/English muffins, lemon trifle (thinking English-y), chocolates, little cookies, toffee, etc.
If someone is very good at baking, could make French macarons, and give as gifts.
Long Island Ice Tea or flowery type liquors. Although breakfast, might want to do mimosas or bellini (If anyone has a vintage tea tray, set up a “bar” on that)
Give packs of organic tea as favors, and make your own labels using a vintage-looking stamp. Can get bulk tea at many healthfood store or chinese markets)
Card games for fun – and if you’re with all close friends make it a card *drinking* game Might be fun to do a bridal trivia “then and now” game about victorian weddings/traditions…
For favors, make DIY fascinators for each girl to wear (instead of hats) and make yourself a pretty bride one.
Here’s the link to the Russian Tea Room in NYC. They have a “high tea” menu: