If the CustPhoto variable is not set to anything when you perform the Update it will overwrite whatever was there with a null. If you don't want to update the Photo in the Table then remove it from the update, like this:
Code:
CN.Execute "UPDATE Customers SET " & _
"FullName= '" & RplS(Txt(1).Text) & "', " & _
"Address= '" & RplS(Txt(2).Text) & "', " & _
"DateBirth= #" & MyDate(PckBirth.Value) & "#, " & _
"Facebook= '" & RplS(Txt(4).Text) & "', " & _
"Email= '" & RplS(Txt(5).Text) & "', " & _
"Phone= '" & RplS(Txt(6).Text) & "', " & _
"Cellular= '" & RplS(Txt(7).Text) & "', " & _
"HairColour= '" & RplS(Txt(8).Text) & "', " & _
"Oxygen= '" & CmbOxygen.Text & "' " & _
"WHERE ID= " & LsVw.SelectedItem.Tag