You can create such gifs via Photoshop (and I'm pretty sure there's other software that allows similar things).
it's pretty easy and quick to make with silhouettes such as the flame or the lotus flower.
Here's my way of doing it (there might be better ways of doing it, but I prefer this method personally); 1.) Go in-game and record the gif you have in mind
2.) Load up photoshop and enable the "Timeline" (via the "Windows" button)
3.) File > Open > Select the gif you recorded/made
In addition, you could remove the unwanted parts from the gif in the timeline (not the actual layers) to reduce the size or to make it loop nicely
4.) Search around for a pattern you like, can be a border or a silhouette (such as the lotus and flame silhouette in the update thread)
5.) Once you have found the pattern or silhouette that's to your liking, you insert it as your first layer in your gif Photoshop file
6.) Select all the gif layers (pro tip: click the first layer of the gif and hold shift while clicking on the last layer of the gif), right-click and select "Create Clipping Mask"
Now your gif is inside the silhouette of your choice.
Move around the silhouette layer if it's not matching your gif properly.
In addition, I tend to use "Inner Shadow" or "Outer Glow" on the silhouette layer to make the gif stand out a bit more.
The PvP customizations are all fully tradable and can be bankshared, however the Champion's Token is untradable but can be bankshared.