
In the traditional Baltic symbol-set known as the raksti, each of the Old Gods has his or her own symbol.
The Sun's is a Sun-Wheel, the Moon's a crescent. Fire has a fylfot (swastika), Thunder a compound fylfot, the Winds an equal-armed cross.
The symbol of the Goddess of Dawn is a Tree. In Latvia, Austras koks, Dawn's Tree, is a popular motif on Easter eggs to this day. (Austra, of course, is sister to the other Dawn Goddesses of the Indo-European world: Easter, Ostara, Aurora, Eos, and Vedic Ushas among them.)
Why would a tree be the emblem of Dawn?
Look East just before Sunrise. There you will see Dawn Herself standing in the sky, making Her Presence known primarily through light and color, attributes difficult to capture in a glyptic symbol.
Hence Austra's Tree. In a given landscape, Dawn first shines Her light on the high points. In low-lying, flat country like the Baltics, these would be the trees.
There's more. Lady of Dawns both diurnal and annual, the Dawn Goddess everywhere is also deemed the Goddess of Spring. What better symbol of Spring than the Tree of Life: sap running, buds enscaled, drawing up abundance from the Earth.