If, instead of switching your worpdress image portfolios to advanced plugins like nextgen, you decide to stick to the original but imperfect native wordprfess gallery, you have a lot of solutions
- Exclude images from gallery in posts allows you to use only a specific set of post images for a post. works by adding a function to impages, that allow to exclude this image from the gallery without deleting it from the post, allowing the insertion somewhere else. Note that this plugin does not use the exclude tag, but it stores a meta data in the database for each image, and filters the gallery output to exclude or not each image from the gallery. Only works for a single gallery, but very efficient.
- AutoNav Graphical Navigation and Gallery Plugin : a good plugin for displaying thumbnails of subpages, a good way of implementing visual subpage navigation
- Galleria plugin is a nice way of implementing slideshows