I would work on angles and perspective.
Instead of just shooting looking straight on at the baby, or doing the famous hospital pic where the baby looks like they are upright, embrace thei mushyness. Cuddle them up in a pillow or even pile of blankets (I use beanbags for my shoots). Get at all different angles. Get the clothes off of the baby (make the room very warm to make for more even toned skin, and a happier baby. Get on the ground and get every different angle and perspective you can with the baby.
Remember, when PP not to make it so the baby's head or body seems like it is tilting down. Always just rotate it slightly up, it makes the viewer more comfortable even if they don't know why.
Watch that double chin. I know it sounds very silly, but it makes a difference in how the baby will appear. They just look prettier and different angles that aren't squished in the face.
Also, use mom/dads arms, body as a backdrop and a poser for the baby too.
Have fun. Great job posting pics of your adorable new nephew!