This is a collection of 12 slides that I think represent the different types of business presentation slides that are out there. Use them to design and calibrate you colours, fonts, and other visual elements. If you get these 12 slides to look good and consistent, any presentation will look good. You can read the full blog post about making PowerPoint slides look elegant here
This bundle is only available in PowerPoint, and in 4:3 format. The individual slides though are taken from the store, where they are also offered in Apple Keynote format, and/or in a 16:9 widescreen layout.