I think dreams could add a lot to imersion in the atmosphere/story/roleplaying with very little programming (considering they are not in the actual game, but when the game is paused).
There could be many types of dreams, here are a few exemples:
-memories from the hero’s past;
-recent important events (memorable images from quests already completed);
-nightmares (for exemple if you have an identified enemy in the main quest, you dream fighting him and you wake up when he almost killed you);
-visions from the future (hints for active or future quests, hints for hidden treasures, etc);
-random dreams, just anything that can be related to the hero: romance (dreaming a beautiful girl you saw at the local tavern can do no harm, eh? ), professions, politics, celebrations, etc.
Of course the dreams shouldn’t trigger everytime you sleep so as not become too repetitive. Maybe have an invisible counter that makes sure you only dream once per week no matter how many times you sleep.
Would be neat when you wake up to get a message that expresses how you feel after what you saw in the dream.
Share your thoughts, would dreams be a good adition to next Tes?