http://www.laptoplunches.com/
This is a good site with lots of ideas.
Keep in mind, Preschool kids/kids don't eat a lot. Generally. So serving size wise, it doesn't have to be a lot. MOST times, the kids do not even eat everything that is in their box. I know, because I"ve volunteered at my daughter's Preschool and Kinder and 1st grade and sometimes now in her 2nd grade, and the kids do not often eat all their food.
Just pack what her favorites are.... that way, you can rest assured that she IS eating. Some kids don't even eat what their Mom packs. So bear that in mind.
Just keep to things you know she will eat and likes.
But stay away from junk food... or candy etc. Believe it or not, many kids go to school with just chips/candy/juice/cookies in their lunch box. I have seen it. Many times. The Teachers don't like that of course.
Go according to what is your daughter's favorite foods... not yours. Because otherwise, kids will not eat, at school, even if hungry. That has been my observation. Or they will give it away to the other kids.
You do NOT have to make "recipes" or fancy lunches. Just straight forward food or left overs from the previous night. No one is judging you about how good a "chef" you are. You just want your child to have something in their stomach, that they WILL eat... so they don't get too tired/over-hungry or fussy for lack of eating at school.
That has been the one thing... which I see ALL the time in kids, and in conjunction with their lunches they bring from home. And then their Moms complain that their kid NEVER eats what they pack for them.
all the best,
Susan