♥ Single/static images: use power-of-two size. Unless you change the setting "downscaling quality" to "high" which forces all exported images to be padded to a power-of-two size.
♥ Sprites with 2 or more frames: any size. Because they'll get turned into a power of 2 sheet.
♥ Tiled backgrounds: power-of-two size.
Unfortunately we have to wait until WebGL 2.0 comes out before this silly power of 2 limitation is removed, however that may happen sometime this year.
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