Purely archeological non-literate Civs are still marginal at best, because in most cases we don't even know what they called themselves and wind up with artificial modern titles for them. That doesn't preclude them by any means, as Civ has played fast and loose with Civ titles forever, almost always choosing Recognition over Accuracy . . .
No matter how you slice it, though, it still leaves a great number of potential Civs that can be reconstructed. And even purely archeological groups, as long as we know 'the shape of their houses' and physical artifacts like pottery decorations (which can yield emblems to identify them by in-game) weapons, tools, burial/religious practices - as stated, the physical record from archeology can yield most of hat is needed to show the Civ 'on the map' and even in Units and iconography.
Urnfeld might be stretching it a bit, but a starting Bronze/Iron Age Scandinavian Civ, since we know their houses, ships/boats, weapons, tools, dress and even some hair-styles (the north European bogs yield amazingly detailed bodies and sacrificed goods) is quite possible as a Starting Point for later Norse, Normans, or Goths.
And in central Asia, in addition to the historical Scythian/Saka Civ, we could easily have the earlier Cimmerians or even the Sintashta or Yamnaya, as well as the Pre-Mongol Xiong-Nu.
Yum.