In oik v2.1 there is a change to the logic that finds the image to display when a full sized image is requested. Previously the routine would randomly select one image from those attached to post. It would not choose the featured image, even if there were no images attached to the post. The new logic, when
thumbnail=fullis being used, is to find the featured image first. Then if there is no featured image select an attached image at random. It is now possible to create a nivo slider for pictorial news – posts in a particular category with featured images being used to display full sized images. Note: You are still required to ensure that there are images somehow attached to each post being displayed in the slider; the code does not ignore posts without images.