Do you have some Lego sets that are broken and missing pieces? You can use those extra pieces you now have as stamps! How about some Indian corn? You know those ears of corn with colorful kernels that people use for fall decorations?
Follow the link for a tutorial on how to make festive Indian corn stamped with Legos!: http://www.craftymorning.com/lego-stamped-indian-corn-craft-kids/