I am not very sure of your question. If your original window is already full sized, then can you get your next window even bigger? If your original window is not that big, then you might try this:
$(".image_id").click(function(){
var url = $(this).attr('target','_blank');
window.open(url, "height=300,width=400");
return false;
});
Which means here the path of href is set to blank.
And also the image_id here is the id of your own image. You need to set the height and width parameters based on the size of the previous window size.