Prize giveaways for a photography company?

[Anon.]

I started my photography company only 4 months ago. I’m looking to increase the amount of Likes on my facebook fan page. I do my main communication for my business through facebook. Once a month I giveaway a prize to gain more “Likes” on my page. I have not gained many new LIKES for my page and just wondered what are some prize ideas that would interest you to like a photography page on facebook. I do not want to give away gift certificates or any of my services, I’ve been doing that already. Maybe some ideas of small priced and large priced items or ideas. Thanks for the feedback!
I already have a website and business cards. Not looking to give away my services. i've been doing that already.