Map Annotations not showing image property on Android.

I have the following code while i am trying to add a simple annotaion:

var ann = Titanium.Map.createAnnotation({
    latitude:lat,
    longitude:lon,
    title:"Message from "+from,
    subtitle:sub,
    animate:true,   
    image: '/images/arrow_right.png',
    rightButton: '/images/arrow_right.png'
});

The image 'arrow_right.png' is placed under /android/images/res-mdpi/arrow_right.png' because i want to have various versions depending on the screen density.

The problem is that the rightButton property is working fine (i see the image specified) but not the image property (i only see a blue dot on the MapView)! This is really strange since both properties have the same value!

Can anyone help me out?

Thanks.