Assuming there is only one table in the document, you could use mail merge processes to speed things up.
With the image already placed in the first cell add the following to duplicate it to the rest of the table. Even with a large table it is pretty well instantaneous.
Code:
Dim oDoc As Document
Dim oFld As field
Set oDoc = ActiveDocument
With oDoc.MailMerge
.MainDocumentType = wdMailingLabels
WordBasic.MailMergePropagateLabel
.MainDocumentType = wdNotAMergeDocument
End With
For Each oFld In ActiveDocument.Tables(1).Range.Fields
If oFld.Type = wdFieldNext Then oFld.Delete
Next oFld