[سعود]

كود :

Imports System.IO

Public Class Form1
   Dim picspath As String = "pics\"
   Dim pics As New List(Of Image)
   Dim pcount As Integer = 0
   Private Function IsValidImage(filename As String) As Boolean
       Try
           Dim img As System.Drawing.Image = System.Drawing.Image.FromFile(filename)
       Catch generatedExceptionName As OutOfMemoryException
           ' Image.FromFile throws an OutOfMemoryException  
           ' if the file does not have a valid image format or
           ' GDI+ does not support the pixel format of the file.
           '
           Return False
       End Try
       Return True
   End Function

   Private Sub Timer1_Tick(sender As Object, e As EventArgs) Handles Timer1.Tick
       If pcount < 0 Then Exit Sub
       pic.Image = pics(pcount)
       pcount = Int(Rnd() * pics.Count)
       Timer1.Interval = 3000
   End Sub

   Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
       Dim dir As New DirectoryInfo(picspath)
       For Each fl As FileInfo In dir.GetFiles
           If IsValidImage(fl.FullName) Then
               pics.Add(Image.FromFile(fl.FullName))
           End If
       Next
   End Sub
End Class

حتى لو لم يعمل المثال المرفق فالكود المكتوب هو كل المطلوب.