Yes I have, I did a Blaidd from Elden ring by a the furry artist/animator Sollyz, at first, with the GIFs alone then I added the images for when the gif stopped loading (I'll go ahead and zip/post it for anyone interested).
What happens if played with just GIFs: The gif would play with minimal problems and clicking on the portrait will continue playing the GIF (or straight up crash, but as the AI goes back and forth with the clothing, sometimes the GIF would reload or need a few more clicks before it comes back up and the GIF would play normally (it's very back and forth))
With images and GIFs: In packs where it has both an image and a GIF, it would switch between the two as intended, however, if the GIF itself crashes, the image would take over and be the only thing playing (I think this is a great way to still have the player stipping even with the GIF crashing and I often make sure every folder with a GIF has an image backup to prevent only seeing a black screen)
The performance of the system: My computer isn't very strong and I often have stuttering when play games as is, however, the game itself will continue playing the game when their is GIFs and typically wouldn't slow down at all, BUT, the game would slow down if the character portrait is clicked one too many times.