Store Locator does have option to resize the markers that appears on the Google Maps as overlays via the shortcode attributes, in order to resize them, use the following shortcode attribute.
[ASL_STORELOCATOR icon_size="30x30"]The above shortcode will resize all the markers on the Google Maps into 30×30 size, the value 30×30 represents the width and the height of the marker that will be scaled into it.
