WordPress.com launched new style layout options for photo galleries that allows users to create magazine-style mosaic layouts. When adding a gallery to a post or page we can select Rectangular, Square, and Circular gallery layouts. Panos (justpi) of WordPress Tips came up a quick method for creating multiple galleries on blogs with themes that support Custom Menus. So get ready to combine the two to make some beautiful galleries featuring your best photos in fine fashion.
Custom Menu Intro
A custom menu allows you to display Categories with drop-downs to sub-categories in tabs along the horizontal navigation where normally only Pages tabs are displayed. If you wish you can also include Pages with drop-downs to sub-pages and/or Tags pages, Posts and/or Custom Links in your custom menu as well. You are in charge of what appears in a custom menu. Note: You choose which to display and which to hide.
Multiple Galleries Walkhrough
To create multiple galleries on the same page or post in a WordPress.com blog are you will need to attach all of the images to the post or page first, and then use gallery shortcodes to designate which images you want included in each gallery.
After you upload the images go to to Media > Library, hover over each image name, note its image ID number at the end of the information displayed in the status/progress bar of your browser, then go to the page editor, switch to the HTML editor, and use the gallery shortcode image ID number for the images you want to include.
Quick Method for Themes with Custom Menus
Panos (justpi) came up with this quick method below for creating multiple galleries on blogs with themes that support Custom Menus. Create a custom menu first so the published dummy pages don’t show up, i.e. you can’t use a draft page to accomplish this trick.
Or you upload the one group of images via the post, upload the rest via a page you’ll create for the purpose, get the ID of the page and use it with the gallery shortcode. This way you’ll only need one ID number instead of many.
But you’ll need to replace the regular top menu of the theme with a custom one, so that the dummy pages won’t show up. Source