If you import images into Decker (via drag-and-drop or Import Image), Decker interprets them as still images, decoding the first frame of GIFs and then applying dithering to convert them to 1-bit. Decker itself does not have any built-in ability to represent animated images.
There are, however, Contraptions that extend Decker with animated GIF playback (among many other things). See the linked thread for several variations on a GIF importer/player, some of which support color. Decker's palette will need to be configured to match the palette you used in WigglyPaint to get all the colors correct when you re-import the GIFs; as long as the images were all made using the same palette, you should be able to simply save WigglyPaint to your desktop, drag-and-drop the deck onto Decker and use the Font/DA Mover to import the "patterns" resource.
While I'm afraid it doesn't help much if you've already saved your drawings as GIFs, for future reference the easiest way to import animations from WigglyPaint into Decker is to not export GIFs, but instead copy the "wiggler" contraption directly from WigglyPaint into decker, as demonstrated in this thread.
Does that make any sense?