<% Layout.image %>
macro renders an image out of the layout imagepool either as plain image, thumbnail, popup or url param.name can contain a slash indicating that the image belongs to a different site or to root

Sourcecode in Layout/macros.js:
1:   function image_macro(param) {
2:      var img;
3:      if ((img = this.getImage(param.name, param.fallback)) == null)
4:         return;
5:      // return different display according to param.as
6:      switch (param.as) {
7:         case "url" :
8:            return img.getUrl();
9:         case "thumbnail" :
10:           if (!param.linkto)
11:              param.linkto = img.getUrl();
12:           if (img.thumbnail)
13:              img = img.thumbnail;
14:           break;
15:        case "popup" :
16:           param.linkto = img.getUrl();
17:           param.onClick = img.getPopupUrl();
18:           if (img.thumbnail)
19:              img = img.thumbnail;
20:           break;
21:     }
22:     delete(param.name);
23:     delete(param.as);
24:     // render image tag
25:     if (param.linkto) {
26:        Html.openLink({href: param.linkto});
27:        delete(param.linkto);
28:        renderImage(img, param);
29:        Html.closeLink();
30:     } else
31:        renderImage(img, param);
32:     return;
33:  }