Add image to TabPanel

I try to add an image to a TabPanel. But the image is not visible in debug mode.

Sub Open() Handles Open
var n as NSTabViewMBS = TabPanel1.NSTabViewMBS
var it as NSTabViewItemMBS = n.tabViewItemAtIndex(0)

// First test with image
var i as new NSImageMBS(wifi)
it.image = i

// Second test with new picture
var p as new Picture(16, 16)
p.Graphics.DrawingColor = Color.Black

var np as new NSImageMBS(p)
var n2 as New NSTabViewItemMBS(“GFX”)
n2.image = np
n2.label = “New GFX”
n2.Enabled = True

End Sub