first of all: NextGen Gallery should not be a problem, I think this plugin works with all themes.
Normally in the page editor you can’t see the images. The idea behind the Quickgallery feature was a fast way to show some pictures. So we’ve decided to create the Quickgallery. But it’s only a fast solution, if you need a hight professional Gallery with many options and settings, you should better choose a gallery plugin.
Here is how the Quickgallery works: Create a new page, choose the “Quickgallery” as page template, then upload the pictures for the gallery (Click ‘Add Media’ Button above the editor), and after uploading the images, close the pop up window, publish the page and all is done. Now the template (on front-end) will search for the attached pictures of this page and display them on the page, thats all.
Editing an existing gallery
Just go to the page of the gallery ( in WordPress admin ), and click again the ‘Add Media’ button above the editor. Then choose the ‘Uploaded to this page’ option in the dropdown. Then WordPress will show you only the attached images to this page / Quickgallery. Now you can sort them with drag and drop, delete some of the pictures or add new one.