Browsing Images from Other Applications in Flare

Can I browse images from iPhoto or Aperture inside Flare? Is there an image browser?

Yes. Press Command-O, scroll down the list on the left side and select Media > Photos, you should see options for iPhoto, Aperture or Photo Booth on the right hand side. You can also adjust the window size here to view more images.

Since Adobe Lightroom is not created by Apple, it doesn't support OS X's built-in Image Browser. As a result, you cannot browse images from that application from within Flare.