He is an approach to easily creating application art for a Windows Store or Windows Phone Store app.
  1. Open PowerPoint 2013
  2. Click the Insert Tab>Click Shapes and pick the rectangle
  3. Click on the empty slide and stretch the shape
  4. Right click on the shape and select Size and Position setting size to be 3.13 high by 6.46 wide
  5. Click insert again and click online picture (or Clip art) and then pick clipart. Choice an image to use and resize it to with a fair amount white space
  6. Click insert again and click on WordArt
  7. Shrink to fit
  8. Drag the cursor to select all the items in your image (e.g. the shape, clip art and WordArt)
  9. Use the key combination CTRL-G to group everything
  10. Right click on the grouped shape and select Save As Picture
  11. Your Art is done!
  12. Open in Paint to select resize to make you image the required size

You can also walk through the video walkthrough. Thanks to my colleague Brian H. Prince for this awesome tip!

How to create application art for a Windows Store or Windows Phone Store app