I think one of the many Maya glyphs would be nice, but I don't know if there's one simbolising the Maya people. The closest I can do for now is to give one referring to one of their main cities, Tikal (the Maya lived in city states, not a unified empire, so it's like I'm giving you a glyph for Athens representing all Hellenes): https://www.famsi.org/research/pitts/MayaGlyphsBook1.pdf, on page 72, maybe the one on the right is the better one (all 4 glyphs mean Tikal, they had many ways to write the same thing).

@Stan` and I have actually started a repo for Empires Besieged here: https://gitea.wildfiregames.com/0ad/empires_besieged.  The last change was 11 months ago, but I'm working on things in DE (Guptas and Sasanians; a big thank you to @Duileoga and @Lopess) which will directly translate to EB at some point in the future. So, whether EB becomes it's own "game" or an "era" or an "expansion" or a "release" is up for debate. I personally advocate for a "0 A.D. Eras" concept, where players can swap between eras (Empires Ascendant, Empires Besieged, Masters of Bronze, Millennium AD) and only play those civs, or choose to play with all civs available at once. 

I would love to have such a feature in the game for multiple things, such as wheat fields. But for now, what I mean is that we can have different variations of the structure so that it will look different sometimes when you build one (like how there are helmet variations). 

Yes, that's totally understandable. Regarding the "multiple actor variations", does that mean one chooses, or could it be that the mound evolves from pebbles to grass with time? That would be nice if possible.

Nice catch. Any suggestions for a more accurate "symbol" representing them?