to let windows handle it is sooooo much easier all you need is this

Code:
Private Sub Form1_Load(sender As Object, e As System.EventArgs) Handles Me.Load
        Timer1.Start()
    End Sub

    Private Sub Timer1_Tick(sender As System.Object, e As System.EventArgs) Handles Timer1.Tick
        Static ctr As Integer = 0
        Dim pics() As Image = {My.Resources._1, My.Resources._2, My.Resources._3, My.Resources._4, My.Resources._5, My.Resources._6}

        PictureBox1.Image = pics(ctr)
        ctr = ctr + 1
        If ctr > 5 Then
            ctr = 0
        End If
    End Sub
save it
get your exe file from the project folder
change the name to <name>.SCR
and thats it

just set your screensaver on windows to your program and it will open and close automatically because windows will do that by itself.