Eu criei umNSOperationQueue para baixar imagens (do Twitter para celular):

NSOperationQueue *queue = [[NSOperationQueue alloc]init];
   [queue addOperationWithBlock:^{
    NSString *ImagesUrl = [[NSString alloc]initWithFormat:@"http://api.twitter.com/1/users/profile_image/%@",[[status objectForKey:@"user"]objectForKey:@"screen_name"]];;
        NSURL *imageurl = [NSURL URLWithString:ImagesUrl];
        UIImage *img = [UIImage imageWithData:[NSData dataWithContentsOfURL:imageurl]];
        [[NSOperationQueue mainQueue]addOperationWithBlock:^{
            if (img.size.width == 0 || [ImagesUrl isEqualToString:@"<null>"]) {
                [statusCell.imageCellTL setFrame:CGRectZero];
                statusCell.imageCellTL.image = [UIImage imageNamed:@"Placeholder"] ;
            }else

            [statusCell.imageCellTL setImage:img];

esta funcionando bem, mas quando parece mover o pergaminho e ver as imagens ainda estão carregando, e eles estão mudando várias vezes até obter uma imagem.

E eu não gosto do diagnóstico Perfil do Tempo, então eu queria de alguma forma fazer issoNSOperationQueue no fundo

Também é possível mostrar como fazer um "Imagecache" não há necessidade de baixar uma imagem já baixada.

** (Status = NSDictionary do Twitter Timeline).

editando: :( All Cell)

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{


    static NSString *CellIdentifier = @"Celulatime";
    UITableViewCell *Cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];


    if ( [Cell isKindOfClass:[TimeLineCell class]] ) {
        TimeLineCell *statusCell = (TimeLineCell *) Cell;
        status = [self.dataSource objectAtIndex:indexPath.row];


        statusCell.TextCellTL.text = [status objectForKey:@"text"];
        statusCell.NomeCellTL.text = [status valueForKeyPath:@"user.name"];
        statusCell.UserCellTL.text = [NSString stringWithFormat:@"@%@", [status valueForKeyPath:@"user.screen_name"]];


        NSDate *created_at = [status valueForKey:@"created_at"];
        if ( [created_at isKindOfClass:[NSDate class] ] ) {
            NSTimeInterval timeInterval = [created_at timeIntervalSinceNow];
            statusCell.timeCellTL.text = [self timeIntervalStringOf:timeInterval];
        } else if ( [created_at isKindOfClass:[NSString class]] ) {
            NSDate *date = [self.twitterDateFormatter dateFromString: (NSString *) created_at];
            NSTimeInterval timeInterval = [date timeIntervalSinceNow];
            statusCell.timeCellTL.text = [self timeIntervalStringOf:timeInterval];
        }

        NSString *imageUrlString = [[NSString alloc]initWithFormat:@"http://api.twitter.com/1/users/profile_image/%@",[[status objectForKey:@"user"]objectForKey:@"screen_name"]];;
        UIImage *imageFromCache = [self.imageCache objectForKey:imageUrlString];

        if (imageFromCache) {
            statusCell.imageCellTL.image = imageFromCache;
            [statusCell.imageCellTL setFrame:CGRectMake(9, 6, 40, 40)]; 
        }
        else
        {
            statusCell.imageCellTL.image = [UIImage imageNamed:@"TweHitLogo57"];
            [statusCell.imageCellTL setFrame:CGRectZero]; 

            [self.imageluckluck addOperationWithBlock:^{
                NSURL *imageurl = [NSURL URLWithString:imageUrlString];
                UIImage *img = [UIImage imageWithData:[NSData dataWithContentsOfURL:imageurl]];

                if (img != nil) {


                    [self.imageCache setObject:img forKey:imageUrlString];

                    // now update UI in main queue
                    [[NSOperationQueue mainQueue] addOperationWithBlock:^{

                        TimeLineCell *updateCell = (TimeLineCell *)[tableView cellForRowAtIndexPath:indexPath];

                        if (updateCell) {
                            [updateCell.imageCellTL setFrame:CGRectMake(9, 6, 40, 40)]; 
                            [updateCell.imageCellTL setImage:img];
                        }
                    }];
                }
            }];
        }


        }
    return Cell;
    }