Shroom, don't forget cheese boxes. They make great risers, and can even be used as deep platters. Best of all, they're free.
Although it sounds weird, consider metal trash-can lids for foods that need to stay cold. Invert the lid (skirting it, if necessary), fill with crushed ice, and lay out oysters, etc.
Garage sales, if you've got the patience for them, can, literally, be gold mines. Somebody else's junk turns into your display treasure.
Develop a contact-network with historic reenactors. They have all sorts of clothing and equipment that you can borrow for an appropriate themed party. Include SCA in that network, as its members are a great source of fantasy gear.
Costume shop owners can often direct you to sources of other props. They tend to be in touch with that sort of thing.
I don't do much catering, hardly at all really and typically just rent what I need. However one time I went to a friends wedding was helping set up chairs and such and the caterer dropped the ball on (can you believe it) tiers for the wedding cake. That's right no tiers for three half sheet cakes designed to look like a castle with moat and surrounding countryside and village. In a brilliant moment I went to the local deli and asked for pickle buckets and got three of them. Then raided the Churches tool closet for a saw. cut two of the buckets into different heights and draped with a table cloth. looked good, no one was the wiser. till tear down and then the caterer kinda got in trouble.
I have a couple of weddings coming up that will be held in barns. Any ideas for props? I have smallish galvanized pails (1 qt) that I have used for beach themed parties and will use them for the barns, but could use a couple of more ideas. Thanks!
Lentil, are you saying that because the weddings are being held in barns that you're looking for a farm theme? And, if so, what sort of farming is most prevalent in the area? That, alone, should provide some clues.
For instance, if I were doing such down here I would decorate with old-style tobacco farming tools: Tobacco baskets, and chopping knives, and spikes, and tobacco sticks, etc. Maybe use a pair of tobacco setters to support tabletops. That sort of thing.
I'm guessing that where you are dairy is the big thing. If that's the case, old-fashioned milk cans, and three-legged spoons, and milking pails would work. Dairy cows are belled, and those would work as props, too.
I know there are miniature, decorative milk cans available. You could use them as centerpiece elements. Lot's of gingham, as it always says "farming." Maybe do the tablecloths out of it?
Canning jars are a great element for a farm theme. Use them decoratively, and for service (drinks, condiments, soups, salads, some apps and desserts can be served right in them). The larger (i.e. half-gallon) can also be used to hold floral displays and as elements in the centerpieces.