About 10 years ago I had my sons pictures taken at a welll-known studio and they used a half egg. He was sitting it it and it looked great; she said that they used it for babies too, and just laid them down in it with padding.
Anyhow, since then I've experimented with making paper mache items, such as a huge cauldron for Halloween. Its the same concept and looks great. Takes a while to make, but essentially its the same thing, and doesn't take much experience.
I've used a small wire fence material as the base, simply shape it into a half circle shape, and then use newspapers and paper bags cut into strips. As you make the egg, remember to make the top of the half circle jagged as though the egg has been cracked open. You can make it however large you want it; its very cute when large enough to seat a toddler.
Once you have it hardened and shaped with the paper mache (and yes, flour and water will work, no need to buy the pre-made expensive kits), you can then use primer, making sure the shape is what you want and the texture is as smooth as you like. Once you have used white primer (to lighten it making it easier to paint), you can can paint it with whatever color you want, probably pastel would be best since its easter.
You can also waterproof it: we have used our cauldron for photos but also for our ourside decorations for halloween. Our cauldron is approximately 4 feet tall and wide, so you can see that its all really up to your imagination! It will take a few days to make but it will be well worth it!