Honoring my DH's late father

Husbands father passed since we had our daughter. He and my husband had a very special relationship (truly best friends) and DH has mentioned that this (birth of our second child) is the first real momnumental moment he'll have without his dad. :,-(
Thinking of ways I could honor/acknowledge his dad during this special time. We do not know the gender of the baby but if it's a boy, we plan to name baby after him. Thoughts or ideas welcome! 
Pic of Papa and our daughter