I usually use http://imgur.com/ for images (same site as SO uses for their inline images) – no sign up required, just upload or paste in an image link and you’re ready to go.

It support CORS requirement so you can link directly and use it with canvas for pixel extraction.

If you need to host different files in addition to image I would suggest DropBox as markE does.

There are restriction however, as with any free service incl. ImgUr and DropBox, so be sure to read the Terms (ToS) of use before using the links (ie. none of them intent to function as a CDN so you might want to check out some commercial CDN providers).

Enabling CORS usage

If allowed you can do this in JavaScript – set crossOrigin before setting src:

var img = new Image();
img.crossOrigin = "";  // or "anonymous", will be interpreted the same
...
img.src = "https://stackoverflow.com/questions/19823469/...";

As attribute for HTML tag (order doesn’t matter):

<img crossOrigin="" src="" ...>

Test

var img = new Image();
img.crossOrigin = "";
img.onload = test;
img.src = "https://i.imgur.com/fHyEMsl.jpg";

function test() {

  var ctx = document.querySelector("canvas").getContext("2d");
  ctx.drawImage(this, 0, 0);
  
  // This will fail if no CORS support, otherwise all OK
  try {
    ctx.getImageData(0, 0, 10, 10);
    alert("All OK");
  } 
  catch(err) {
    alert("No CORS support...");
  }
}

<canvas></canvas>