it's my understanding that new users can't post more than one link, in order to avoid SPAM. I assume the same is true for images. Can/should we as editors override these restrictions for in cases where we feel it's beneficial? For example, adding a second link here or linking the two screen captures here?
Yes, it's fine. As you say, the reason for prohibiting low-rep users from posting links and images is fear of spam. If you read the question and decide that it's okay to post the link/image, then there's no fear of the link/image being part of a scripted spam attack*.
*Unless you are Skynet, in which case we have bigger problems anyways.