When you’ve uploaded photos or images into a gallery in the nextGEN photo gallery plugin for WordPress, you’ll find that many of the auto generated thumbnails are not quite centered as you might like them. Here’s a short tutorial on how to modify your displayed thumbnails …
Log-in into WordPress,
on the left side of your dashboard, select “Gallery”,
then, from the drop down menu, select “Manage Gallery”,
from the Gallery listing on the right, select the Gallery that you want to work on,
scroll down the Gallery page to a listing of your image thumbnails in the gallery,
point at a thumbnail that you would like to center and you’ll see a menu of available operations,
select “Edit Thumb”,
in the pop-up edit window, place the cursor on the image and click/drag to select an area,
this area can be re-located and/or re-sized as desired,
Click on “Up-date” and close window,
Repeat as necessary!