Random PictureBox

[dday9]

Well, store you picturebox's in a list(of <t>). Then use the random class to generate a random integer from 0 to that list's count in a timer's tick event with the interval set to 1000. Finally toggle that item's visibility. Here is an example, not tested, free handed:

Option Strict On
Option Explicit On

Public Class Form1
   Private pb_List As New List(Of PictureBox)
   Private r As New Random
   Private shown As Boolean = False

   Private Sub Form_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Form1.Load
      'Loop through each picturebox on the form
      For Each pb As PictureBox In Me.Controls.OfType(Of PictureBox)()
         pb_List.Add(pb)
      Next

      Dim tmr As New Timer
      tmr.Interval = 1000 '1 Second

      'Event Handler
      AddHandler tmr.Tick, AddressOf Timer_Tick

   End Sub


   Private Sub Timer_Tick(ByVal sender As Object, ByVal e As EventArgs)
      'Static, not dimmed
      Static i As Integer
      If Not (shown) Then
         i = r.Next(0, pb_List.Count)
      End If
      
      'shown is now what it wasn't then
      shown = Not (shown)

      'If shown then the pb is visible, and vise versa
      pb_List.Item(i).Visible = shown
      
   End Sub

End Class

Like I said, I free typed this and didn't test it, but it gives you an idea.