Hi Kelly,
It is possible to show images in lists, but on a custom form, the closest workaround is to use a descriptive text parameter (e.g. "Related Image"), which -- although it won't support an embedded image such as this:
<iframe src="https://giphy.com/embed/xT5LMQ8rHYTDGFG07e" width="480" height="366" frameBorder="0" class="giphy-embed" allowFullScreen></iframe><p><a href="https://giphy.com/gifs/season-3-the-simpsons-3x11-xT5LMQ8rHYTDGFG07e">via GIPHY</a></p>
you can at least set the text to "Copy and paste the following link to see the image: https://giphy.com/gifs/season-3-the-simpsons-3x11-xT5LMQ8rHYTDGFG07e", or (in case it suits your workflow), you could also paste it (or "them") into the description of the object in question (e.g. Project, Task, Issue, etc.) which -- perhaps a happy oversight -- is the one place will render the link as clickable.
Regards,
Doug