Some cardstock, glue, spools of ribbon, and those nifty little double-sided scrapbooking rounds to bring my Legos to life, and voila! I added some multi-colored streamers and balloons and I had my backdrop.
I made a few extra Legos and glued them onto some colored paper bags I found in the party aisle at Walmart. One of my party favors was inspired by the Lego banner. I duplicated the same pattern, but just made them a little bit smaller.