Powerpoint is my most favorite and world renowned software for making presentation by Microsoft and even though it has plenty of free templates that you can customize for Office Work or School presentation. However If you want more creativity then you can find some stunning Free PowerPoint templates at Templatewise they have tons of free templates that you would most probably find suitable for your presentation in every topic. There are various options to choose the template you can categorize it topic wise or popluarity wise either way it should sever the puprose.! Do let me know what you think of it!