Upload Image browser widget for drupal 6
Try FileField Sources module 


  FileField Sources is an extension to the FileField module. The
  FileField module lets you upload files from your computer through a
  CCK field. The FileField Sources module expands on this ability by
  allowing you to select new or existing files through additional means,
  including:
  
  
  Re-use files by an auto-complete textfield 
  Attach server-side files uploaded via FTP 
  Transfer files from a remote server (cURL required)
  Paste a file directly from the clipboard (Drupal 7 only) 
  Select existing files through the IMCE file browser
  



the first one is what youre looking for.