Which mtg card which is not a reprint would have the most reprensentative image of the theme from the set antiquities?
The card that most represents the theme of the antique set, Urza's Tower. Part of a cycle known as Urza's Lands (which also includes Urza's Mine and Urza's Power Plant), this card is symbolic of the set's focus on artifacts and ancient, powerful machines.

The Tower of Urza artwork depicts the towering structure of the ancient kingdom of Thran, a central part of Ancient Set's history. The series is based on the war between the brothers, the conflict between Urza and Mishra, and Urza's lands represent the powerful resources they used in the war.

In terms of gameplay, Urza's lands have a unique mechanic where by controlling all three different lands you can generate a large amount of colorless mana that can be used to cast important powerful items in the set.

Please note that the specific artwork may vary as the card is printed in multiple sets and each set may have its own version of the artwork. The original Antiquities version was illustrated by Mark Poole.