MKMapView: Instead of Annotation Pin, a custom view

Here's an answer on Swift 3. It dequeues annotation view if possible or creates a new one if not:

func mapView(_ mapView: MKMapView, viewFor annotation: MKAnnotation) -> MKAnnotationView? {
    // Don't want to show a custom image if the annotation is the user's location.
    guard !(annotation is MKUserLocation) else {
        return nil
    }

    // Better to make this class property
    let annotationIdentifier = "AnnotationIdentifier"

    var annotationView: MKAnnotationView?
    if let dequeuedAnnotationView = mapView.dequeueReusableAnnotationView(withIdentifier: annotationIdentifier) {
        annotationView = dequeuedAnnotationView
        annotationView?.annotation = annotation
    }
    else {
        annotationView = MKAnnotationView(annotation: annotation, reuseIdentifier: annotationIdentifier)
        annotationView?.rightCalloutAccessoryView = UIButton(type: .detailDisclosure)
    }

    if let annotationView = annotationView {
        // Configure your annotation view here
        annotationView.canShowCallout = true
        annotationView.image = UIImage(named: "yourImage")
    }

    return annotationView
}

Swift 2.2:

func mapView(mapView: MKMapView, viewForAnnotation annotation: MKAnnotation) -> MKAnnotationView? {
    // Don't want to show a custom image if the annotation is the user's location.
    guard !annotation.isKindOfClass(MKUserLocation) else {
        return nil
    }

    // Better to make this class property
    let annotationIdentifier = "AnnotationIdentifier"

    var annotationView: MKAnnotationView?
    if let dequeuedAnnotationView = mapView.dequeueReusableAnnotationViewWithIdentifier(annotationIdentifier) {
        annotationView = dequeuedAnnotationView
        annotationView?.annotation = annotation
    }
    else {
        let av = MKAnnotationView(annotation: annotation, reuseIdentifier: annotationIdentifier)
        av.rightCalloutAccessoryView = UIButton(type: .DetailDisclosure)
        annotationView = av
    }

    if let annotationView = annotationView {
        // Configure your annotation view here
        annotationView.canShowCallout = true
        annotationView.image = UIImage(named: "yourImage")
    }

    return annotationView
}

When you want to use your own image for an annotation view, you should create an MKAnnotationView instead of an MKPinAnnotationView.

MKPinAnnotationView is a subclass of MKAnnotationView so it has an image property but it generally overrides that and draws a pin image (that's what it's for).

So change the code to:

-(MKAnnotationView *)mapView:(MKMapView *)mV viewForAnnotation:(id <MKAnnotation>)annotation 
{
    MKAnnotationView *pinView = nil; 
    if(annotation != mapView.userLocation) 
    {
        static NSString *defaultPinID = @"com.invasivecode.pin";
        pinView = (MKAnnotationView *)[mapView dequeueReusableAnnotationViewWithIdentifier:defaultPinID];
        if ( pinView == nil ) 
            pinView = [[MKAnnotationView alloc]
                                         initWithAnnotation:annotation reuseIdentifier:defaultPinID];

        //pinView.pinColor = MKPinAnnotationColorGreen; 
        pinView.canShowCallout = YES;
        //pinView.animatesDrop = YES;
        pinView.image = [UIImage imageNamed:@"pinks.jpg"];    //as suggested by Squatch
    } 
    else {
        [mapView.userLocation setTitle:@"I am here"];
    }
    return pinView;
}

Notice that animatesDrop is also commented out since that property only exists in MKPinAnnotationView.

If you still want your image annotations to drop, you'll have to do the animation yourself. You can search Stack Overflow for "animatesdrop mkannotationview" and you'll find several answers. Here are the first two:

• Is it possible to call animatesDrop in a MKAnnotationView rather than MKPinAnnotationView?
• How can I create a custom "pin-drop" animation using MKAnnotationView?