// Make sure file is removed from the iCloud image backup system
AppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
[appDelegate addSkipBackupAttributeToItemAtURL:imagePath];

// Removes all application assets that are not user created from the iCloud backup system
// by adding the NSURLIsExcludedFromBackupKey to every file that is downloaded and stored
// in the application's document directory
-(BOOL)addSkipBackupAttributeToItemAtURL:(NSString *)fileString {
    
    // Convert string path to NSURL
    NSURL * fileURL = [NSURL fileURLWithPath:fileString];
    
    // Make sure file has already been created before applying key
    if (![[NSFileManager defaultManager] fileExistsAtPath:[fileURL path]]) {
        NSLog(@"File Missing: %@",[fileURL path]);
        return NO;
    }
    
    // Obtain iOS version for proper key application
    NSString *currSysVer = [[UIDevice currentDevice] systemVersion];
    
    // 5.0.1 requires <sys/xattr.h>
    if ([currSysVer isEqualToString:@"5.0.1"]) {
        const char* filePath = [[fileURL path] fileSystemRepresentation];
        const char* attrName = "com.apple.MobileBackup";
        u_int8_t attrValue = 1;
        int result = setxattr(filePath, attrName, &attrValue, sizeof(attrValue), 0, 0);
        NSLog(@"Excluded '%@' from backup",fileURL);
        return result == 0;
    }
    // Above 5.0.1 use NSURLIsExcludedFromBackupKey key
    else if (&NSURLIsExcludedFromBackupKey) {
        NSError *error = nil;
        BOOL result = [fileURL setResourceValue:[NSNumber numberWithBool:YES] forKey:NSURLIsExcludedFromBackupKey error:&error];
        if (result == NO) {
            NSLog(@"File '%@' could not be excluded from iCloud backup set. Error: %@",fileURL, error);
            return NO;
        }
        else {
            NSLog(@"File '%@' has been removed from iCloud backup set.",fileURL);
            return YES;
        }
    } else {
        // iOS version is below 5.0, no need to do anything
        return YES;
    }
}