EXCEL

Add a Picture to a Comment

1. Right-click the cell that contains the comment.
   (or choose Insert Comment)
   
2. Choose Edit Comment, and clear any text from the comment.
   
3. Click on the border of the comment, to select it.
   
4. Choose Format>Comment
   (or Ctrl+1)
   
5. On the Colors and Lines tab, click the drop-down arrow for color.
   
6. Click Fill Effects
   
7. On the picture tab, click Select Picture
   
8. Locate and select the picture
   
9. Click Insert, click OK, click OK
   

Also:

Charles Maxson has some code that will place a picture in the comment box based on the contents of a cell.

" Imagine that you have a list of parts for a product and you want to assign them to cells... then your users could see them as they hover over the cells."

Excel: Code to add picture to Excel Comment

Mary Ann Richardson, on TechRepublic.com, suggests saving a graph as a JPG and using that as a picture in a comment.

Add an Excel chart to a comment

Embedding a picture within a document or spreadsheet can enlarge the file size. If you are trying to email that document, it may bounce back for being large. You may want to try a pdf converter, to get a smaller file size. Excel to PDF works wonders and once it is transmitted, extract the data with an PDF to Excel converter to
get the spreadsheet back into an editable format.