How to replace default red-dot.png in maps API V3 using markerclusterer after zooming into single marker?

I am using MarkerClustrer. After sufficiently zooming in on markers, they are separating out, but the image is default red-dot.png that google provides. Is there way I can change that default? I am not asking 开发者_运维问答to how to change the cluster icon, but the marker icon after zooming in!!