"Took a screenshot, cropped the girl and started recoloring, pixel after pixel to make it look like a true *.gif, adding and/or removing pixels where necessary. This may or may not look exactly like the sprite used in-game, I don't give a toss.

UPDATE: I just realised that Steam, being Steam, upscales the whole thing to make it fit your screen resolution, and thus turns it into an eyesore of a picture. Just click on the art to open it in a new tab/window and you'll see it the way it's supposed to be seen."