When Zack Snyder shared a photo of Wonder Woman holding the decapitated heads of her enemies during the Crimean War, it was clear this photo existed before Patty Jenkins' Wonder Woman. Her film not only depicted the Amazonian arriving on Earth long after the Crimean War, but also showcased her as a warrior driven by love, not savage rage. Therefore, Snyder's photo doesn't sense in the current DCEU. The timeline does not match up, nor does the violent nature of Snyder's photo represent Gal Gadot's just and compassionate Wonder Woman.
However, Gadot's Diana Prince only applies to the current DCEU. Thus, there are multiple means through which Snyder's head-chopping Wonder Woman could exist outside of that continuity — possibly in a different part of the multiverse.
Alternate Continuities
A violent version of Wonder Woman might exist in one of the many alternate continuities associated with the DCEU. Both Joker and The Batman take place in worlds separate from the main canon, so the Diana in the Snyder photo might live there. With WB and DC further exploring other possibilities for their characters, it is possible a more swords-and-sorcery inspired version of Wonder Woman — in line with Brian Azzarello's New 52 interpretation —could materialize in contrast to the more loving version played by Gal Gadot.
Flashpoint Wonder Woman
It's rumored that the upcoming The Flash film will draw inspiration from the Flashpoint comics where Barry encounters an alternate reality with Michael Keaton's Batman. This opens the door to an alternate version of Wonder Woman, especially considering Gal Gadot is reportedly going to be in the film.
It's possible the DCEU continuity will be "ruined" thanks to Flash venturing into the multiverse, and the aggressive Wonder Woman Zack Snyder originally conceived can exist in this continuity, especially if The Flash draws from Flashpoint. In these comics, Wonder Woman is driven to conflict against Aquaman, resulting in a war between the Amazonians and Atlantians. If the battle is featured in The Flash, a more brutal Wonder Woman will be brought to the big screen.
Another factor that could result in an aggressive Wonder Woman is if she were to be introduced to mankind not through Steve Trevor, but through a far more treacherous conflict — possibly through Barry opening the multiverse.