I'm 28, I like mature writing and I am female.
Hmm let's see. For relationship ideas M X F.
I'd be interested in Spy X Spy; rival spies who are attracted to one another. (think Mr and Mrs Smith)
Dragon Rider X Princess of the Kingdom in which he protects. (kind of FF4 based)
Your Human X My Elf. Can be medieval era or futuristic sci-fi where my people are elves on a planet. I have one sci-fi idea where we are both rulers of our respective planets and are on opposing sides of a galactic war but they can bring peace to the galaxy through unity.
Hero X Heroine. I would use my angelic/Valkyrie type superhero for this one. Very action packed!
I also like Knights of Camelot, just throwing that out there too :)