Is your elementary school a feeder school for one or more local high schools? Get the prospective high school(s) involved in your auction with a "spirit" basket donation.
Local high schools are always looking for ways to win over future students. Grade school kids (and their parents) love sporting items from their prospective "next step." From t-shirts to water bottles to pens - everything goes over well.
For fall auctions, high schools are in their recruiting stages and your auction is full of potential attendees and a great way to get the word out; for spring auctions, your grade school kids will love to get a jump on their high school spirit and show-off where they are headed. Either way, its a great promotion for the high school and a popular item for your silent auction.