I love the idea of using a cookie sheet with a lip and spreading it with soil and wheat berries, spraying it with water, allowing the wheat to sprout into wheat "grass" then putting a spring bough in water on it, letting the bough bud and hanging little eggs from it. All from Heaven on Earth.
I think any sort of baby animals are springtime themed - espec whatever is native to your area. For us birds like robins and geese and bluebirds return. Forcing bulbs or buying some potted ones is fun for spring too.