How can I upload multiple images all at once?
See the Plupload integration module. From the project page:


  Provides integration between for the Plupload widget to upload
  multiple files and Drupal. Plupload is a GPL licensed multiple file
  uploading tool that can present widgets in Flash, Gears, HTML 5,
  Silverlight, BrowserPlus, and HTML4 depending on the capabilities of
  the client computer.