There will be as many styles and designs in a sketchbook as there are individual art and design students. There are also no rules to how a sketchbook has to be produced. The way you work in the sketchbook will depend on personal preference. Some students like to keep it very neat and tidy and others prefer a more raw approach. Most importantly, your sketchbook should reflect your personality.
Try talking to your teacher and asking if they can show you sketchbooks from previous years to get an idea of what to include. You teacher may also have some guidelines on how they expect material to be submitted for assessment.
What is important about sketchbooks is that they maximise the amount of evidence you can demonstrate of your creative process. Some students get side-tracked by working on large colourful titles to pages, and while it may make it more presentable, you have to consider whether it will contribute to the project. If you are decorating, are you developing a valuable skill, does it make the page of the sketchbook easier to view, or is there a more efficient way of presenting information.
Students can often spend more time decorating a title on a sketchbook page than actually undertaking work that will contribute to their grades. As visual people, it is understandable that they want it to look good, but they need to learn how to balance time spent on presentation with genuine investigation and the development and production of ideas.