Нарисовать на форме сетку, а при нажатии заменить на картинку

Dim draw As Graphics = PictureBox1.CreateGraphics
        draw.Clear(PictureBox1.BackColor)
        For i = 0 To PictureBox1.Width Step 35  
            draw.DrawLine(Pens.Black, i, 0, i, PictureBox1.Height)
        Next
        For i = 0 To PictureBox1.Height Step 35  
            draw.DrawLine(Pens.Black, 0, i, PictureBox1.Width, i)
        Next

Private nH As Integer = 20  'число ячеек по горизонтали
Private nV As Integer = 20  'число ячеек по вертикали
Private ln As Integer = 20  'размер ячейки
Private cll(nH, nV) As Label
Private Sub Form6_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
    Panel1.Height = ln * (nH + 1)
    Panel1.Width = ln * (nV + 1)
    Panel1.Location = New Point(5, 5)
    Me.ClientSize = New Size(Panel1.Width + 10, Panel1.Height + 10)
    For i = 1 To nH
        For j = 1 To nV
            cll(i, j) = New Label
            Panel1.Controls.Add(cll(i, j))
            With cll(i, j)
                .BorderStyle = BorderStyle.FixedSingle
                .Width = ln
                .Height = ln
                .Left = (ln * i) - ln
                .Top = (ln * j) - ln
                .Text = ""
                .BackColor = Color.FromArgb(&HFCF9C5)
                AddHandler cll(i, j).Click, AddressOf CellClick
            End With
        Next
    Next
End Sub
Sub CellClick(ByVal Cell As Object, ByVal e As EventArgs)
    Dim lb As Label = CType(Cell, Label)
    If lb.BackColor = Color.Black Then
        lb.BackColor = Color.White
    Else
        lb.BackColor = Color.Black
    End If
End Sub

Public Class FormMain
….
Private isDo As Boolean = False
….
Private Sub PictureBox1_MouseDown(sender As System.Object, e As System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseDown
    isDo = True
    setAction(e.Location, e.Button)
End Sub
Private Sub PictureBox1_MouseUp(sender As System.Object, e As System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseUp
    isDo = False
    PictureBox1.Refresh()
End Sub
Private Sub PictureBox1_MouseMove(sender As System.Object, e As System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseMove
    setAction(e.Location, e.Button)
End Sub
Private Sub setAction(pp As Point, btn As MouseButtons)
    Try
        Dim j As Integer = pp.Y \ aa
        Dim i As Integer = pp.X \ aa
        If btn = Windows.Forms.MouseButtons.Left Then
            grid(i, j) = A.Clone
        ElseIf btn = Windows.Forms.MouseButtons.Right Then
            grid(i, j) = B.Clone
        End If
    Catch ex As Exception
 
    End Try
End Sub
End Class

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        PictureBox1.Image.Save("E:\45564.png")
    End Sub

Imports System.Drawing.Drawing2D
Public Class FormMain
…
Private isSaveImg As Boolean = False
…
Private Sub PictureBox1_Paint(sender As System.Object, e As System.Windows.Forms.PaintEventArgs) Handles PictureBox1.Paint
…
    If isSaveImg Then
        Dim im As New Bitmap(PictureBox1.Width, PictureBox1.Height)
        Dim gg As Graphics = Graphics.FromImage(im)
        For i = 0 To nn - 1
            For j = 0 To nn - 1
                gg.DrawImage(grid(i, j), New Rectangle(i * aa, j * aa, aa, aa))
            Next
        Next
        im.Save("c:\00\img.png", Imaging.ImageFormat.Png)
        isSaveImg = False
    End If
End Sub
…
Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
    isSaveImg = True
    PictureBox1.Refresh()
End Sub
End Class