If they do make a reverse Sejuani skin I want it to be a joke on the people who want a reverse Sejuani skin. Rather than the boar riding Sejuani, it should be Sejuani riding the boar as normal, but the boar moves in reverse the whole time and both are looking back over their shoulders as one would when going backward in a car. Add construction equipment beeping sounds during her Q (which would of course also go backward).
PS Vandal Sejuani where. Put her in a full motorcycle helmet and armor with a proper hog, and make her flail a cinder block on a chain.