|Not sure this is what you want, but you could try using a Comment Box for the picture.|
First, Add a comment to the cell, but remove any text.
Next, right click the border of the comment and select Format Comment.
Pick the Color and Lines Tab
From the drop down box labeled Color select Fill Effects
Select the Picture Tab then browse for the desired picture.
Double click on your pretty picture and resize as needed.
You might also want to change the behavior of the comment, buy setting it to "Indicator only, and comments on hover", that way the picture will only appear if you hover or pass over the cell.