Are you wanting to make the food or have people help you or wanting to buy the food?
I have a neat book that is called Classroom Treats. It has recipes for a variety of classroom snacks:
There is dipped, drizzled and decorated pretzels. bananna split cupcakes, reese's haystacks, polar bear banana bites, mini pizza cookies, ultimate rocky road cups, peanut butter chips and jelly bars, cookies that look like the sun called Sunshine Butter cookies. They have unusual cakes, brownies, cookies, and very creative. Not sure if you have help or if you are doing this all by yourself.
If you are wanting to buy things- what about getting help from a bakery. Bluebonnet Bakery in Fort Worth has great cookies in various shapes/sizes and if you have a theme, they could help you out with your theme. You might want to have mini sandwiches, you could do sausage biscuits, bisuits and ham, cheese and crackers, chicken nugget tray from Chick Fil A, you could hire a caterer, if you have the extra money. What about cantelope and get a melon scoop and scoop out cantelope and honey dew,etc.. What about strawberries dipped in chocolate.
I know that Kung Fu movie is coming out this summer with the Panda Bear. You could do a theme around that. You could do a beach party theme, with umbrellas, water, beach toys,etc...
That's all I can think of right now. I would try and get some help from other parents if you can or even the teachers might help also. Good Luck and let us know how it goes.