Unfortunatly almost directly after I posted this message and went back to VS I accedently found the texturebrush and after a quick test I found that that was also the answer to the question. For completeness I'll post a example of a textured Polygon:
Code:
Protected Overrides Sub OnPaint(ByVal e As System.Windows.Forms.PaintEventArgs)
MyBase.OnPaint(e)
Dim myBrush As New Drawing.TextureBrush(My.Resources.TestTexture, Drawing2D.WrapMode.Tile)
Dim myBox As Point() = New Point() {New Point(0, 0), New Point(300, 0), New Point(300, 300)}
e.Graphics.FillPolygon(myBrush, myBox)
End Sub
Easy as pie.
I am still amazed how complete GDI+ is, it is almost Direct3D :P.