Updates

Tables in PowerPoint are bascially Word tables. Avoid pasting tables as pictures.

Inserting a Picture into a Table

When you add a picture to a table it is actually layered on top of the table rather than being placed inside it.
You can resize the table to fit the picture.

When you add a picture as a fill effect. It is resized to fit the cell and may be distorted.
Resize the cell to remove any distortion.