The way I have solved it is in the shutter/shutter-reloaded.css and shutter/shutter-reloaded.js
in the CSS I have changed the attributes of “#shDisplay div#shPrev” and “#shDisplay div#shNext” (line 28+) to:
#shDisplay div#shNext{
float:right;
position: absolute;
right:10%;
top: 50%;
}
#shDisplay div#shPrev {
float:left;
position: absolute;
left:10%;
top: 50%;
}
In the JS I have changed lines 110 and 119 to
prevlink = '<a href="#"><img src="wp-content/plugins/nextgen-gallery/shutter/button_left.png"></a>'+dv;
and
nextlink = '<a href="#"><img src="wp-content/plugins/nextgen-gallery/shutter/button_right.png"></a>'+dv;
and uploaded 2 nice arrows into plugins/nextgen-gallery/shutter/