Sharepoint URL field as Picture?

 Hi there, I'm pretty new to ASP.net and Sharepoint. I have searched google and MSDN for over half an hour to find an answer but was not successful. Since this is my fist post and I'm also not sure if i'm in the right forum here so please don't be to harsh to me . This is the fact, I'm trying to create a Sharepoint List pure by C# code not the Sharepoint Editor! Now I have a problem with the field types on one of my lists. When I add a new field with the
SPFieldtype.URL this way:
 
SPListItem newItem = list.Items.Add();
newItem.Fields.Add("Portrait", SPFieldType.URL, false);
 
it is displayed on the 'page' as link...as it should be. But when I create a new field in the Sharepoint editor it has the property to display the image of the picure and not the link.
So what code or property is needed to display the Picture itself and not the URL i ...