Then use the ImageCombo's ComboItems collection's Add method to add new items to the ImageCombo.

Private Sub Form_Load()
Dim i As Integer

    ' Attach the ImageCombo to the ImageList that
    ' holds its pictures.
    Set ImageCombo1.ImageList = ImageList1

    ' Create some items.
    For i = 1 To ImageList1.ListImages.Count
        ImageCombo1.ComboItems.Add , , _
            ImageList1.ListImages(i).Key, i
    Next i

    ' Select the first item.
    Set ImageCombo1.SelectedItem = ImageCombo1.ComboItems(1)
End Sub