Change
If ckbox.Selected = True Then

to
If ckbox.Checked Then

I think that's what you want.

HTH

Now, instead of a single byte, you have to pass a byte array to procedure
Private Function SaveToDB(ByVal imgname As String, ByVal imgbin As Byte(), ByVal imgcontenttype As String) as integer
...

Correct syntax is
Dim imgbinarydata(imglen - 1) As Byte

Since arrays are zero-based, you use imglen - 1 to get an array with imglen elements.

You should check that...