We are told not to talk to the dead... Not necessarily that it's impossible, but that we shouldn't. Perhaps for our own protection. Maybe they really aren't who we think they are (i.e. demons posing as our loved ones). We are supposed to consult only God, not the dead:
"When they say to you, 'Consult the mediums and the spiritists who whisper and mutter,' should not a people consult their God? Should they consult the dead on behalf of the living?" Isaiah 8:19 (NASB)
"There shall not be found among you anyone who makes his son or his daughter pass through the fire, one who uses divination, one who practices witchcraft, or one who interprets omens, or a sorcerer, or one who casts a spell, or a medium, or a spiritist, or one who calls up the dead. "For whoever does these things is detestable to the LORD; and because of these detestable things the LORD your God will drive them out before you." Deuteronomy 18:10-12 (NASB)
If you see something, that's fine... but I wouldn't take it to be of God... or even of what it appears to be.
-Michael