One nice, relatively little-known feature in the Galleria theme is the ability to setup secondary navigation to sub-collections right below your collection title. This feature is shown in action below:
To set this up for any of your own collections, simple go to Online Store > Navigation and create a new menu that has the same name as the collection you want to add it to. In the example shown above, we created a menu called Tech Bags and added links to Backpacks, Duffels and Totes, Messenger Bags, and Sleeves as shown below.
Once saved, this menu will appear below your collection title automatically! As you may or may not know, Shopify doesn't officially support nested or sub-collections, so this is a great way to provide your customers with another way to narrow down their product choices in large collections.