Here are some (opinionated) styleguides for AngularJS applications, I recently found on github. They are (currently) work-in-progress / living documents: (ordered by stars)
- https://github.com/mgechev/angularjs-style-guide
- https://github.com/johnpapa/angularjs-styleguide
- https://github.com/toddmotto/angularjs-styleguide
These style guides may give you a reference for the structure of your next AngularJS project.