PowerPoint - Linked image automatically update

In Powerpoint, when you insert your picture, make sure to select Insert and Link option.

With this option, the picture is embedded in the presentation. However, when you open the presentation, Powerpoint checks to see if the file the link points to is newer than the embedded copy. If so, it automatically updates to the new file.

So, whenever you update your pictures, don't forget to open your PowerPoint file for the update to occur.