Apologies for this late reply, I do hope I'm still in time for this seminar...!
Towards the end of your paper, you cited the example of the World Guangong Culture Promotion Association and their choice of image of Guangong:
The standing image of Guangong chosen to brand the World Guangong Culture Promotion Association shows the god standing and striding confidently forward (Figure 11). In this conspicuously cleaned up version of more traditional depictions of the deity, all traces of armor and glittering gold have been removed. The green of the robe is a paler, more subtle hue than the the blue or green of the more traditional representation. The overall green tone of the image may reflect, I speculate, current “green” concerns with the state of the global environment.
While he does carry his halberd, this version of the god has a warm, modern look, more like a prosperous businessman striding forward to shake your hand than a model of warrior virtues. The “magic” in this image is no longer the traditional ling but instead, I suggest, the economic miracles to be expected from doing business with China.
Whilst I have no empirical evidence to disprove your suggestion that the "green" image is a reflection of environmental concerns, might I suggest that the significance of this (selected) representation is actually the removed "traces of armor and glittering gold" -- to portray a certain image of "modernity" (not necessarily a concern with the environment). Guangong's armor might possibly be perceived as a relic of an "unmodern", "feudal" past, where violence is closely related to justice, whereas "gold" has increasingly become associated with tackiness, lack of class, or backward notions of affluence and status.
Abstraction and formalization assert unimpeachable authority. Conversely, however, concrete representations, and especially those that take a full-figured anthropomorphic form, render the gods approachable, transforming them into patrons with whom it is possible to form particularistic relationships in which both emotion and exchange can be used to secure the gods’ favor.
Surely there are greater politics at play in the production and reproduction of certain representations, some which have survived, some which have changed over the years. The particularistic, patron-client relationships that you are proposing seem limited to existing adherents of the said religion, but does not seem to take into account a broader politics of religion that involves not just its followers, but its leaders and experts (such as Taoist masters, monks, and people who are involved in the daily management of religious bodies, institutions, and sites of worship).
To put it crudely, gods look the way they do, not just because their followers want them to, but also because that might be a specific public image that its followers would like to portray to non-adherents, or adherents with whom that "religion" is starting to lose influence with. (And this has specific implications for the symbolic power of their god/deity if follower count drops.) Chinese popular religion has often been associated with descent, lineage, and familial practices, but -- forgive my gross generalisations here -- its original medium for continuity is starting to give way because people's social lives are becoming less and less influenced by what their parents believe in, for instance. Its continuity might also be explained in terms of people who want it to continue -- and therefore select certain sorts of representation to attract or maintain interest and/or belief. In the case of the Guangong Culture Promotion Association, its existence seems to be borne of a specific mission to spread the greatness of Guangong Culture transnationally, especially to Chinese communities that have become alienated from Guangong, and the way the association chooses to portray Guangong of course is strategic to those purposes.
The strategic representation of gods and deities is not necessarily always a reflection of its adherents' personal relationships or interpretations of the religion, or their beliefs and hopes, but also of a greater politics that cannot be ignored. It could be about attracting more tourist dollars, or attracting more donors so that the temple will not have to be shut down. It could be about portraying a deity as superior to another deity.
A disclaimer: I'm only an undergraduate student, so my suggestions are obviously rather "unprofessional" and likely to be ill- informed. I've only had some engagement (at undergraduate level) with the anthropology of China and ontological anthropology, so my response is probably a lot less refined and academic than everyone else's here. This was a knee-jerk response to your paper, and most of it stems from my personal experiences as a Chinese Singaporean, raised in an environment with a combination of Buddhist practices, ancestral worship, Taoist rituals, and a hodgepodge of other things that have also been cast under "Chinese popular religion".
Thanks for the great paper, John, it was very thought-provoking! I hope OAC Seminars continue :)