I don't think there's any harm in looking up toward heaven and saying, "Mom, I miss you"; "Mom, today was your birthday, and I thought about you all day. I can't wait until I get to see you again!"; etc. We can also ask God to tell our departed loved ones that we miss them, or to give them a special message from us. It certainly doesn't hurt to ask Him. But that's different, of course, than trying to make some kind of contact with them in an occult way through pathways in the spirit world. Those ways only lead to deception and darkness.