You can use Flash Catalyst to create galleries, for example a scrolling list of thumbnails that display larger images when clicked. Here are some tutorials that explain how:
Create a photo gallery (using list interactions), on the FlashCats blog
Create a data list component -- Don't let the title scare you, a "data list" is a really powerful component to get to know better; it enables creation of very creative visual things like galleries. When you need repeating items, consider using a data list.
