Not sure if this would help but if your looking for simple and unexpected, Ill share what I did when I proposed...
She had been wanting to get married for a while and even though I had just bought the ring I still acted hesitant, dropping hints that I may propose at the end of summer which was about 7 or 8 months away. Now we are college students, and I had a friend who was a photography major. So I had one of my wife's roommates say that she knew a girl who was doing a project for her major, and needed to take some pictures of "a couple". My wife's roommate then explained that she had told this girl that she had a roommate who was dating a guy and they would probably love to volunteer. So she gave this girls number to my wife, and my wife called the photographer and set the whole thing up. I planned ahead with the girl that was taking the pictures, and told her to say she would be available on 3 different days... 2 of which I knew my wife was busy, and 1 I knew she had wide open. So my wife sets up this appointment and then begs me to go and have our pictures taken for some student working on a project. I of course reluctantly agree. Our campus has about a one acre garden for the horticulture department which is ideal for taking engagement pictures, so I had the girl set it up to meet here there. We walked around to a few different areas taking pictures in different poses, then when we got to certain location, I told her I loved her, got down on one knee, pulled out the ring and proposed.
Now we are both pretty simple, low maintenance people, and I wanted something both semi-private, as well as memorable. This way it was a BIG surprise to her, it was pretty private, and we still have professional pictures of the whole thing. My wife didn't see it coming at all because she thought she was the one who set the whole thing up.
Hope this helps, and best wishes to you!