It's best to add pictures, WordArt, or other objects after you've created your table and sized the cell that will contain the object.
To resize either the table cell or the object you've added, select the item you want to change and use the Resize pointer that appears when you move the pointer over the frame boundary.
Note To keep the object and table together when you move them, select both the object and the table, and then click Group on the Arrange menu.