Such a cute idea! You could use almost anything as a topper, old toys or decorations. Just paint it and the lid one solid color. Great way to separate small toys into plastic jars with lids. Just glue the type of toy that goes in that bin and paint.
All you need is some jars with lids, small plastic animals, superglue and spray paint. Glue the animals to the lid with superglue and spray the whole lid with paint. Let it dry and you have the cutest jars ever.