ASIHTTPRequest is a wrapper for network APIs and very easy to download a file. Here is an example of them (but you can do it on the iPhone too - save the images to a “drive” and then upload them.
ASIFormDataRequest *request = [[[ASIFormDataRequest alloc] initWithURL:url] autorelease];
[request setPostValue:@"Ben" forKey:@"first_name"];
[request setPostValue:@"Copsey" forKey:@"last_name"];
[request setFile:@"/Users/ben/Desktop/ben.jpg" forKey:@"photo"];