Here are some of the ideas:
Dragon shapeshifters: Dragons are real but have the unknown ability to change into a human form. Dragons have always found their lifelong mates in other dragons, realized after their first kiss. What happens when a Dragon Lord finds his mate in a human girl?
Arranged Marriage Ideas: Two feuding kingdoms have lost their heirs in the war. Through some crazy idea, they agree to marry their royal magicians, male and female. The problem is neither magician can stand the other. One king is crazy and evil and is only using the marriage to kill off one of the magicians to weaken the other kingdom. Chaos and unlikely romance ensues.
Also, two shape-shifting communities have born a blood feud for centuries. Between the Arians (bird shape shifters) and the Reptilians (snake shape shifters, feel free to rename their clan), many lives have been lost in countless wars. When they call a temporary truce and go to the wisest of the shifters (tiger shifters), they are told to wed their royalty for peace.
Long Lost Friend: Two people grew up together, living across the street from each other. When the girl disappears one day, the boy sells his soul to the darker side to gain power to search for her, suspecting foul play. Years later, after he has ensconced himself in his new life, she returns to her childhood home. Secretly she is a Guardian, or an angel type being who is sent to areas to protect the innocent from demon/darkness. And her childhood friend has killed off three of her brethren before she herself was assigned to the area. What happens when they discover each others identities?
I'm sure I have more. :)