Create a Best-Seller Cover for my new Thriller!

CALIXTO AFIUNE

Hello guys. My name is Calixto Afiune, from Brazil. It's a very special moment to me, as I'm almost ready to publish my first book. One of the few steps remaining is, of course, the cover for it. I just stumbled upon 99 Designs and it's just what I needed. I am very excited about this whole contest! Think about a dream coming true. =)
The title is "A Luz Que Entra Pela Janela", which means "The light that enters through the window", or something like that. Let me just give you guys an idea about what is the book.

It's a thriller, detective novel. It happens simultaneously in two time periods, and I always compare it with "Lost" and its flashbacks.
In the present, detective Marco Lobo is a lonely, alcoholic private detective, who lives waiting for something to happen in his boring life. He doesn't have friends or near relatives, and he misses a woman called Natália, although it's not specified if they were married or not, and if she left him or died. The title refers to him remembering a specific scene with Natália, when the sun is coming through the window when they are waking up in the morning, and she stares at him with her beautiful green eyes as he tries to sleep five more minutes before going to work. This memory comes to him twice or three times during the book, whenever he sees a light coming through a window.
He usually investigates love affairs, but this time there's a different client. Her name is Camilla Sales, member of one of the most powerful families in the city of Terranova, the Sales, involved in a series of fellonies. She doesn't have a usual request, either. She saw one of his cousins, a young man called Oscar Sales, stealing a valuable jewel of the family, and she doesn't want any involvement of the police in this investigation.
He follows Oscar through the city, and they end up in a pawn-shop, where he is supposedly trying to sell the jewel. Unfortunately, Marco can't take any photos of the negotiation, that apparently doesn't happen. Oscar then leaves through a narrow alley, and starts to run after turning a corner. After Marco turns the corner himself, he finds an old foe, ex-cop Roberto Silva, stabbed in the back of a bar. It's a trap: the knife is Marco's, and probably has his fingerprints on it.

In the past, Marco Lobo is an investigator rising inside the police corporation. More so after solving the case of a famous murdered attorney by a small detail that remained unnoticed by everyone else. He and his partner Álvaro Bianchini then begin to investigate the bizarre murder of entrepeneur Tony da Mota, found buried alive in the busiest public garden in Terranova. He doesn't know it yet, but this case is going to change his life forever.

The book then comes and goes back and forth through the timelines until they meet, in the end.

The book is going to be published online, through a Brazilian publisher similar to Amazon. The format is ePub, and I am a newbie at this, I really do not know the size of it. The title must be in Portuguese, "A LUZ QUE ENTRA PELA JANELA". Author: CALIXTO AFIUNE.

I thought a lot about the cover, but I haven't made up my mind about it yet. I am very open minded about it, though. Though the title doesn't sound like a thriller book, the cover HAS TO. So, nothing about a beautiful green eyes girl on the bed, please.

Things that could be on the cover (I AM VERY OPEN MINDED TO NEW IDEAS):
- light coming in through a window, with a sinister feeling to it. No knives or blood, but a silhouette or something like that;
- a panel with the map of a city, full of needles, and photographs of missing people, and notes. Maybe the light coming through the window would fit here as well;
- a guy laying in a dark alley, stabbed in the chest (too cliché, maybe?)
- a dusty, abandoned, private detective office (the light from the window? and maybe the title of the book in blurred lines over the door, as if it was the detective's name. You know what I mean? It has to be kinda creepy as well.)
If something else comes up, I'll let you know. But I'm pretty sure these options got it covered. I don't know for sure, but I will when I see the right one.

I'll give you as much feedback as I can. Let's do this!
Thank you all in advance.