Typically I will use the WordPress Lightbox 2 plugin to provide a format for images within posts on a WordPress site. Basically this plugin provides an ajax window that images open in and you can scroll between the images with mini arrows to the left and the right side or you can close the image with a close button that appears at the bottom right of the image display. You can also change any of this appearance easily through the various CSS files included with four different default themes with Lightbox 2. While working on a WordPress site earlier tonight I ran into an issue where the lightbox 2 image pop up was falling behind the body content. The fix ended up being easy but it needed to be pointed out for others to fix quickly.