Show activity indicator in SDWebImage

This fork has support for this functionality. Take a look at the diff.

But, in general, you can do it rather easily without using that fork:

__block UIActivityIndicatorView *activityIndicator = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:activityStyle];
activityIndicator.center = imageView.center;
activityIndicator.hidesWhenStopped = YES;
[imageView setImageWithURL:[NSURL URLWithString:@"http://www.domain.com/path/to/image.jpg"]
               placeholderImage:[UIImage imageNamed:@"placeholder.png"]
                        success:^(UIImage *image) { [activityIndicator removeFromSuperview]; }
                        failure:^(NSError *error) { [activityIndicator removeFromSuperview]; }];

[imageView addSubview:activityIndicator];
[activityIndicator startAnimating];