Thank you so much for that - Something simple yet very annoying!
I was using:
Me.BackgroundImage = Image.FromFile(App_Path() & "Images\" & imageNames(i - 1))
and changed it to:
Dim newImage As Image = Image.FromFile(App_Path() & "Images\" & imageNames(i - 1))
Dim formGraphics As Graphics = Me.CreateGraphics
formGraphics.DrawImage(newImage, 0, 0)
newImage.Dispose()
And now it works beautifully!