One of the big new features of InDesign CS6 is the ability to create "Linked Content". This feature allows you to have “parent” content that is linked to “child” content that can appear in several places in a single document, or spread across several documents. When the parent content is edited, you are given the option to update the content in all the other locations. You can learn more about this feature here.
But even if you don't care at all about Linked Content, there is one by-product of this new feature that affects almost everyone, in a good way. If you have your Frame Edges shown (View > Extras > Show Frame Edges), each linked image in your layout will display an icon in the upper-left corner. The icon indicates whether the image is linked, modified, or missing. This icon provides 3 benefits:
1. If the image is modified or missing, you can single-click on the icon to update the image or relink to a new image. This saves a trip to the Links panel!
2. If you hover over the link icon, the filename of the image is displayed.
3. If you option/alt click on the icon, the Links panel is opened and the image is selected in the links panel.
You can learn more about Linked Content and all the other new InDesign CS6 features in my new eBook the InDesignSecrets Guide To What's New In InDesign CS6. In this low-cost PDF eBook, I clearly describe how to use all the new features of CS6. You can purchase and download the eBook here.