composer is ignoring installer-paths configuration

Of course, what Danack has said is true: the composer-installers plugin only supports a select list of package types.

In response to that, I have written an extension for the composer-installers plugin which allows any arbitrary package type to be handled by the "installer-paths" directive.

Simply require oomphinc/composer-installers-extender in your composer.json and add support for any additional arbitrary package types:

"extra": {
  "installer-types": ["library"],
  "installer-paths": {
    "special/package/": ["my/package"],
    "path/to/libraries/{$name}/": ["type:library"]
  }
}

For packages that don't specify a type, use the default type library.

From the documentation.

You cannot use this to change the path of any package. This is only applicable to packages that require composer/installers and use a custom type that it handles.

From one of the packages you're installing:

{
    "name": "smottt/wideimage",
    "description": "An open-source PHP library for image manipulation. (With namespaces, PHP 5.3+)",
    "homepage": "http://wideimage.sourceforge.net",
    "type": "library",
    "license": ["GPL-2.0","LGPL-2.1"],
    "version": "11.02.19",
    "autoload": {
        "psr-0" : {
          "WideImage" : "lib/"
        }
    }
}

So basically the package you're trying to install doesn't support custom install paths.