A lot of different artist have contributed to this game. There was once a RA art contest. There's still a bunch of non canon images up on HF from it. The game has been around for years after all.
The most common artists are
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,
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, and
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. If I remember correctly, that picture you listed is by
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back in version 4.4 of the game. (Sometime in 2019; I can't remember every date or changelog of the top of my head). If you like his artwork he also did some scenes for two of the RA DLCS: Emek's rest and Vesper's Booty. If for some reason I'm misremembering, the only other artist that has semi-realistic art style close to Deathmask would be Mikiron.