UPDATE (Feb 20, 2011): #1 and #2 below no longer apply to the CSS. #3 below is still applicable.

UPDATE (Jan 2, 2011): I’m no longer using the below-stated NextGEN Galleryview plugin by Alex Rabe. Instead, I’m using WordPress NextGen GalleryView by John Brien because it has fewer JS conflicts.

http://nextgen-gallery.com/templates/galleryview/

1. To customize the display size of images “within” the NextGEN GalleryView gallery, alter:
– File: nggGalleryview/galleryview.css
– (approx) Line 57:

.galleryview .panel img { width: 400px; height: 230px; }

2. To customize the overall size, colors, etc of the NextGEN GalleryView gallery itself:
– File: nggGalleryview/view/gallery-galleryview.php
– (approx) Lines 40-51:

panel_width: 400,
panel_height: 300,
frame_width: 40,
frame_height: 40,
transition_interval: 0,
overlay_color: '#222',
overlay_text_color: 'white',
caption_text_color: '#222',
background_color: 'transparent',
border: 'none',
nav_theme: 'dark',
easing: 'easeInOutQuad'

3. Fixing the monster-sized right arrow when using Thematic Theme Framework for WordPress: http://www.cozmoslabs.com/2010/01/13/wordpress-photo-slideshow/?cid=3259#comment-3259

– File: nggGalleryview/galleryview.css
– Add the following line at the end of the CSS file:

.galleryview .nav-next { width:22px !important; float: none; }

Extra: Sorting the gallery images