Here are two ways...

This link describes how to create a splash screen userform on which you
could display the logo image:
http://www.xldynamic.com/source/xld.xlFAQ0007.html

Or, you could do something like the following:

Add the logo image to a blank worksheet in the workbook. Turn off the
gridlines
on the sheet (Tools >> Options >> View. Uncheck Gridlines, then click OK.)
Name the sheet MsgSht. Paste the following code in the ThisWorkbook module:

Private Sub Workbook_Open()
Sheets("MsgSht").Visible = xlSheetVisible
Sheets("MsgSht").Activate
Sheets("MsgSht").ScrollArea = "A1:O31"
Application.Wait Now() + TimeValue("0:00:03")  '3 seconds
Sheets("MsgSht").Visible = xlVeryHidden
Sheets("Sheet1").Activate
End Sub

Change Sheet1 to whatever sheet should be displayed after the warning.
Adjust the ScrollArea setting, if necessary.

If you are new to macros, this link to Jon Peltier's site may be helpful:
http://peltiertech.com/WordPress/2008/03/09/how-to-use-someone-elses-macro/

Hope this helps,

HUtch