How to customize a specific position and size for a responsive image in the slider?

Yes you can specify your own backround-position and background-size for any responsive image in the slider to override the Ninja Slider's default settings:

• background-position:

  The data-image attribute will be used to set the background image of the slide. The background image's default style:

  background-repeat: no-repeat; background-position: 50% 50%;

  You can override them with your own styles, eg.

  <li><div data-image="/img/1.jpg" style="background-position:50% 30px;"></div></li>

• background-size:

  By default the responsive background image will adapt to its container in the style background-size:contain;. You can override it with your own specifications. For example:

  <li><div data-image="/img/1.jpg" style="background-size:cover;"></div></li>

  <li><div data-image="/img/4.jpg" style="background-size:auto 200px;"></div></li>

  Learn more about CSS3 background-size