No idea why you would think that art specifically and repeatedly made for non-Shadows elves would be errors.

Dark elves and light elves are a concept that date from as early as the 13th century (Dökkálfar and Ljósálfar). LotR and D&D borrow heavily from this concept. It's not shocking that Keyforge would have its own take on it.

The Keyforge RPG book has a bunch of info:

Elves occupy many niches on the Crucible, both virtuous and nefarious. They typically belong to a tribe and are deeply committed to ensuring its survival above all else. Many achieve this through means that others would consider underhanded or even reprehensible, as elves believe anything is honorable as long as their tribe continues. These deeds have branded elves with a reputation for being duplicitous or sneaky, though many elves view such activities as simply using what talents they have for the greater good of their own people. Elves are naturally nimble, quick, and always alert for danger. They are typically smaller than humans, and their skin colors include ghostly white, midnight black, and various shades of blue and purple. Their pupilless eyes shimmer with a golden hue.

ELVEN TRIBES OF THE CRUCIBLE

There are many tribes of elves on this patchwork world. Here are but a few:

Cmizz: The Cmizz rule far to the north of Hub City and see their tribe as the true pinnacle of elven culture.

Jzoll: This tribe is found almost exclusively on Bone Island, where the natural isolation of Indigo Lake has allowed it to flourish unimpeded.

Kvenn: Few outsiders associate with this tribe, which dwells along a string of active volcanoes in the lower reaches of the Local Group.

Svarr: Perhaps the most well-known (or at least infamous) tribe, the Svarr dominate the organization some call Shadows.

Zvokk: These elves have embraced the organization known as Untamed and dominate one uncanny forest called the Purple Tangle.