Well then you've done something wrong because here's my code:
VB Code:
  1. Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
  2.         For Each ctl As Control In Me.Controls
  3.             If TypeOf ctl Is MdiClient Then
  4.                 ctl.BackgroundImage = Image.FromFile("C:\Documents and Settings\All Users\Documents\My Pictures\Sample Pictures\Winter.jpg")
  5.                 Exit For
  6.             End If
  7.         Next
  8.  
  9.         Dim child As New Form
  10.  
  11.         child.Text = "Child"
  12.         child.Size = New Size(150, 150)
  13.         child.MdiParent = Me
  14.         child.Show()
  15.     End Sub
and here's my form: