Lovely selections - I wonder at the similar characterizations of the two men of Emmaus in many of these paintings, one young, and the other elder bearded and balding.
From scripture there is nothing specific about ages, but I’ve always had the thought that they were two younger men, and that upon Jesus ‘no longer being with them’, they got up and not just returned, but beat feet back to Jerusalem! At least a good five mile race-walk :)
None of these artists ventured it, but I've seen speculation that the pair was actually a couple: Mr. & Mrs. Cleopas. As you observed, Scripture does not identify them--beyond describing their foolishness and slowness.