I am using ASIHTTPRequest to work on facebook graph API.
This is the nearest I have gone to posting a picture on the feed. So if I have a ASIFormDataRequest *request = [ASIFormDataRequest requestWithURL:url];
The url is https://graph.facebook.com/me/feed
Now to post a picture I do the following:
[request setPostValue:@"My Message" forKey:@"message"];
[request setPostValue:@"somepic.png" forKey:@"picture"];
[request setPostValue:@"Some Name" forKey:@"name"];
[request setPostValue:@"Some description" forKey:@"description];
[request startAsynchronous];
If you try this then everything works fine other than the picture being posted. A blank placeholder for the picture is though show on the feed.