Is there a way to find out if images (assets) are landscape or portrait?
How about just using the getHeight() and getWidth() methods available on the AssetFileModel? Something like this:

{% set myImage = entry.imagesField.first %}

{% if myImage.getWidth() &lt; myImage.getHeight() %}
  {# portrait #}
{% elseif myImage.getWidth() &gt; myImage.getHeight() %}
  {# landscape #}
{% else %}
  {# square #}
{% endif %}