(Option 1) Distorted Images
Right-click Image > Format (Picture Tools) > Crop > Choose 'Fill' to fix your problem.
(Option 2) Add Image in Icon/Vector Graphics
To make your presentation more interesting, you also can use vector icon as an image placeholder.
- Select the icon you want
- Copy and paste into your project
- Enlarge your icon
- Select your icon and right-click
- Choose Format Shape
- Fill (Picture & Texture Fill)
- Insert picture from file
Make sure your icon or vector is grouped before adding an image.
If your picture looks like picture No. 3 (Step 4), try turning on 'Tile picture as texture’.
It's not a real solution, but since it works to make your pictures better, you can use this way.