As far as album art. I have a mental picture…
The fall equinox is the beginning of the movement toward the winter solstice. In European mythology this is the beginning descent of the sun into darkness.
Others write better than I…
The symbolic sacrifice of the god at the sabbat of Autumn Equinox, or Mabon, is part of the fertilization process for the future spring planting season. For us today this is a time of cutting away what we no longer need or have moved beyond. There are a few variaof harvest customs from around the world that call the last sheaf standing in the fields the “old man.” I wonder if this is a link to the sacrificial harvest king? Overall, the “old man” was treated much less gently than the corn mother or corn child, for here, in the spirit of the harvest, the god gives up his life at the harvest to feed his people.
As the final crops and fruits are collected, the god, represented by the weakening sun, returns to the earth to rest with the goddess until it is time for him to be reborn again. Sometimes this is referred to as the sun god going into the seed or being held within the grain. At harvest-tide, a time of incredible bounty spreads out across the land. The grains were full of the life and energy of the god, the earth mother rewarded us with her bounty, and finally the crops were all harvested. The fruits of the fields were gathered and then safely stored away.
from longer article
http://www.dailyom.com/cgi-bin/display/librarydisplay.cgi?lid=242