SOURCE: http://www.xtremevbtalk.com/showthread.php?t=90685
Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal _
hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, _
lParam As Any) As Long
Private Const WM_PASTE = &H302
Sub InsertPictureInRichTextBox(RTB As RichTextBox, Picture As StdPicture)
' clear the clipboard
Clipboard.Clear
' Copy the picture into the clipboard.
Clipboard.SetData Picture
' the position of the picture
RTB.SelStart = 4
' paste into the RichTextBox control
SendMessage RTB.hwnd, WM_PASTE, 0, 0
End Sub