Can't argue with that, and you may occasionally have to do it again (basically whenever new card art is added to beta, check the news feed on main menu. If the 'bug' happens very occasionally in-game, assume it's because the opponent hasn't downloaded new art to local files.
Really should be baked in, but ¯\_(ツ)_/¯

That fixed it, Ninja Sloth. But it's a shame that I have to manually "fix" the game as opposed to an error prompting me to download the art (which should really be automatic).

Have you tried settings, then 'download all' on the bottom left?