How can I get the picture of a Facebook event using server side code?

I'm writing a web app that pulls events data from Facebook, and I can get a lot of the information using an app token, but not the picture, which requires a client token, as documented here: http://ift.tt/1BOUuFo

I want the code that grabs the event data to run automatically on a server at regular intervals, without requiring a user to log in to their Facebook account.

Is there a way I can get a client token without user intervention? If not, is there another way I can get the event picture?

This is the code I am using to get the event data, using C# and JSON.Net (This gets a list of events created by the specified user - ResortStudios):

var fb = new FacebookClient();
dynamic result = fb.Get( "oauth/access_token", new
{
  client_id = "XXXXXXXXXXX",
  client_secret = "XXXXXXXXXXXXXXXXXXXXXXXXX",
  grant_type = "client_credentials"
} );
 var apptoken = result.access_token; 
fb = new FacebookClient(apptoken);
result = fb.Get("ResortStudios/events");

JObject events = JObject.Parse(result.ToString());
JArray aEvents = (JArray)events["data"];
string s = aEvents.ToString();
List<fbEvent> lEvents = JsonConvert.DeserializeObject<List<fbEvent>>(s);