Beware: Google often looks at the request to see if that's a regular browser doing the request, a special browser, or some automated mean.
I tried your URL from Processing, and I got a response for a Wap browser... Only one image in it.

I had time to look closer at your code and I found several problems.
First problem: you use append()! See Why use ArrayList instead of array with append()? for details.
More seriously, when using append(), you start with an empty array, otherwise the first item will remain empty.
Other problem: img is one of the XMLElements with no children!
Other issue: you compare strings with ==. See the String reference why you must no do that.
Here is a fixed version of your code:

1. XMLElement xml;
2.  
3. PImage[] imgs = new PImage[0];
4. 
   
5. void setup() {
6. // Unchanged
   
7. }
8. 
   
9. XMLElement printRecursive(XMLElement x) {
10.   if (x.getChildCount() == 0) {
11. //    println(x); //debug
12.     String name = x.getName();
13.     if (name != null && name.equals("img")) {
14.       String url = x.getString("src");
15.       println(url);
16.       if (url.length() > 0) {
17.         imgs = (PImage[]) append(imgs, loadImage(url));
18.       }
19.     }
20.     return null;
21.   } else {
22.     for (int i=0; i < x.getChildCount(); i++) {
23.       printRecursive(x.getChild(i));
24.     }
25.     return x;
26.   }
27. }