[Plugin: NextGEN Gallery] Can I center thumbnail images?

Howdy. Love this plugin and have used it often. I’m building a site for a quilter and I’ve gotten my gallery ALMOST good. However, the thumbnail images seem to be left-justified over the centered description text below them. Is there some way to center them so they don’t look so lopsided in their columns?

Here is a link to the gallery page:
http://artquilts.co/gallery/

Thanks!
Geoff

http://wordpress.org/extend/plugins/nextgen-gallery/