The media browser in Pages '09 is now inoperable after the 10.10.3 update with Photos. There is an iLifeMediaBrowser plugin that Pages 09 used, that was stepped on by the Photos update, and now Pages '09 fails to find a compatible version of the preceding plugin, and fails to show any media content.
Although the Photos application automatically transferred your iPhoto/Aperture libaries, it does not mean that these applications were removed, or cannot be run alongside Pages '09. I just launched iPhoto, and dragged/dropped a photo onto Pages '09 without issue. Copy/paste is supported too. Pages '09 also supports drag/drop of images from the Finder, or from its Insert > Choose… menu item.