If you use Sprite or Tiled Background's 'Load image from URL' it can load off the web, even in preview, providing the server sends the 'Access-Control-Allow-Origin: *' header. The node-webkit object can load files off disk, but they would have to be data URIs in text files!
Most cases where people need lots of images, they're doing something wrong (e.g. the player has 100 weapons, so they draw all 10 player animations again for each weapon, resulting in 1000 animations... when you could just make the weapon a separate object and position it by the player). Try not to use so many images. If you have to, just use project files, what's wrong with them?