I managed to get it to work only in Safari (version 11.0.1), and not in Chrome, only using a 250x250 GIF to view the animated GIF and the outdated THREE.ImageUtils.loadTexture
var materialTextured = new MeshBasicMaterial( { map: THREE.ImageUtils.loadTexture('mygif.gif'); });
and then on render (), you call
materialTextured.map.needsUpdate = true;
jsfiddle (GIF animation only works in Safari!)
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