Can you try uploading it to the repository and then using an html property to display it? You may look in this thread for an example of displaying an html image, I don't see why an animation wouldn't work when a similar approach is used. Re: ThingWorx Grid Widget Questions
Thanks Pai. Your suggestion lead me in the right direction to the final solution. In fact, I've come up with two different workable approaches.
To save everyone else the pain of the discovery process...
Create a file repository and upload your images (use the File Repository Home Mashup from the TW marketplace to make this easy - https://marketplace.thingworx.com/tools/file-repository-home-mashup)
... Use the LoadImage service of the file repository linked to a Value display widget to display the image. More info can be found here (Loading image file in thingworx repository to image widget in mashup)
... Use the GetFileListingWithLinks service and bind the downloadLink return to an Image widget.