I have had problems showing images (animated gif) with image viewers and am now showing them as components in an HTML/JavaScript file that is the one loaded in the webviewer.
The problem here is that in X, you do not have the webviewer string that would allow sending the path for the image itself to the HTML file (I am doing that in Classic, which has a webviewer string).
I have seen some people suggesting that the X thunkable application and the HTML file could exchange information through Firebase or other, which I cannot personally vouch for never having done it myself.
One thing that perhaps could be worth trying is downloading the jpg file as a local file using a generic name, which is then referred as a static resources in the HTML file even though the content varies.