I think that you will need to determine the screen resolution then do some sums based on the size of the image.
The following code will return the monitor's settings:
'place these statements at the top of your code
Declare Function GetSystemMetrics Lib "user32" _
(ByVal nIndex As Long) As Long
Const SM_CYSCREEN As Long = 1
Const SM_CXSCREEN As Long = 0
Dim lWidth As Long
Dim lHeight As Long
lWidth = GetSystemMetrics(SM_CXSCREEN)
lHeight = GetSystemMetrics(SM_CYSCREEN)
MsgBox "Screen Width = " & lWidth & " " & "Screen Height = " & lHeight
I'm not sure how you are planning to display the logo. If on a userform then this illustrates how to make a userform fill the screen:
Private Sub UserForm_Activate()
Me.Top = .Top
Me.Left = .Left
Me.Height = .Height
Me.Width = .Width
The above code goes in the userform's code module.
I hope that the above is the sort of thing you are after!