devtrackers.gg
This doesn't really look consistent with other default card arts styles and might be some lore key art like this
You are correct in that this is not Card Art. :) The official Card Art for Morgan Le Fay is part of the Patch Badge that was tweeted a little earlier, for those curious: https://twitter.com/SMITEGame/status/1397206280842907660
Edit: Clarification
Can confirm: This is not any of her Card Arts :)