From Excel 2002 onwards you can enter an image, probably a logo, into the header or footer of your worksheet. This code enables you to create a macro that will automate the addition of the logo to every sheet in your workbook.
'created 10/01/2008 by Angela Wolff
Application.ScreenUpdating = False 'stops the flashing
Dim WS_Count As Integer
Dim I As Integer
' Set WS_Count equal to the number of worksheets in the active workbook.
WS_Count = ActiveWorkbook.Worksheets.Count
' Begin loop.
For I = 1 To WS_Count
ActiveSheet.PageSetup.RightHeaderPicture.Filename = _
"C:\Document\hhnt_007528.jpg" 'obviously change this to the image and path of your desire.
ActiveSheet.PageSetup.PrintArea = ""
.RightHeader = "&G"
NB. The With End With code is only really required if you are going to change a number of parameters at once.