The library, no matter your project type, is a great resource! You can use it to get ideas for your diagram projects! You could go to a local library or talk to your school librarian. You can tell the librarian what your project is about and they can help you locate books about it!
This image explains what a label is and shows an example of a labeled diagram of a cat.
A cross-section diagram is different from a labeled diagram because it shows the inside of something. See this cross-section diagram of a pumpkin as an exampled!
Interested in making a diagram of a fruit? This video shows a variety of fruits and what their cross section looks like.
Interested in making a diagram of an animal? National Geographic Kids has lots of information on different animals to help you pick which animal you want to make your diagram of.