Generally, I don't like letters or numbers to be used as symbols. There's too much room for misinterpretion, jokes, etc. I'm not even sure I fully endorse the pig as a symbol. Is Horace the only textual evidence for that? I know the statue is from Herculaneum. T
There's also the Boscoreale cup with the pig at Epicurus' feet, plus the leaping pig from herculaneum, which is probably one of the most definitive connecitons. -
I find the pose of the Boscoreale pig surprisingly similar to the Herculaneum pig.
"The Boscoreale Treasure is a large collection of exquisite silver and gold Roman objects discovered in the ruins of the ancient Villa della Pisanella at Boscoreale, near Pompeii, southern Italy." So, they're both from the same general area and same time but still, I find that similarity fascinating.
I find the pose of the Boscoreale pig surprisingly similar to the Herculaneum pig.
agreed and I hadn't noticed that myself. But I am not sure there is much variation in the appearance of pigs(?)
then roared back onto the backs of cars in the 1970s
Seems to me like it also started showing up on some Western European storefronts.
That said, I do have a small plastic piglet on my desk at work
That's cute 😁
Two stylized Ps back to back = Pleasure and Pain
That only works in English, so I don't think it would be a very good idea. Greek and Latin are languages too, of course, but they hold a different status, in my opinion. (As do proper Names, like Epicurus, Ἐπίκουρος.)
agreed and I hadn't noticed that myself. But I am not sure there is much variation in the appearance of pigs(?)
They can be newborn, piglet, or adult. Boar or sow. Boars might show tusks. Sows might be pregnant or have visible teats. Position could be lying, wallowing, standing, or leaping. Could be furry or bare skinned, and fat, lean, or medium. So…there is /some/ variation, but of course they'll still be pigs 🤷♀️
But regarding the leaping piglet, I'm not convinced mammals can be stylised like a fish? There's Picasso's bull sketch (Le Taureau), but I'm quite certain that if didn't have his name attached, it would be considered utterly unremarkable. Plus, for a symbol, there's no symmetry or anything in it -- unlike the Christianist's stylised fish, which is quite geometric as a shape. A pigs face would be an easier, more symmetrical shape overall.
I think it is interesting there never was a symbol other than the bust, which I'm sure not just anyone could afford to own or put on display.
I think it is interesting there never was a symbol other than the bust, which I'm sure not just anyone could afford to own or put on display.
I don't know if any of the ancient philosophical schools had symbols as we think of them: Stoics, Academics, Peripatetics, Pythagoreans, Cyrenaics, and so on and so on. Maybe they had no need. If you wanted to be a student of a school, you knew where to go in your city. I believe all the schools though had statues and busts of their founders in prominent places. Cassius Correct me if I'm wrong, but isn't their reference to Epicureans in particular going around with Epicurus face on rings, cups, etc, as if it's an idiosyncrasy of the school?
I am not sure there is much variation in the appearance of pigs(?)
That leaping posture in both of them seems too similar to be coincidence to me, but granted, that's only two data points.
A sideways rhombus with a dot in the middle would still make use of all the interpretations offered for the ⟐ symbol. It can be found ready-made without being prohibitively expensive, but it isn't a common fashion item in and of itself. This makes it more distinct, ensuring those who use it are much more likely to do so because of this particular meaning. The two products I linked to are more feminine, but I think with different styling, it would work equally for men. It is more reminiscent of an eye than the ⟐ symbol with 90° angles, giving more weight to the interpretation: "Sic fac omnia tamquam spectet Epicurus." In effect, benevolently saying some thing like: "I might not be the Hegemon in the flesh, and I might not be a fully-fledged bust of him, but I am one of his eyes, and I am – figuratively, metaphorically – watching the actions of the wearer, such that they might find it easier to act wisely," invoking (figuratively/metaphorically/psychologically/subjectively) a sense of a benevolent presence, if you will, without losing any of the other interpretations: the atom, the void, the four lines of the tetrapharmakos, and all the other things which have already been mentioned early on in this thread.
Correct me if I'm wrong, but isn't their reference to Epicureans in particular going around with Epicurus face on rings, cups, etc, as if it's an idiosyncrasy of the school?
And because this variant of a sideways rhombus would entail a stylised aspect of the bust / face, it would connect to the historical tradition of showing the bust / face.
I think it really hits that sweet spot between being a simple geometric shape, yet still carrying meaning through symbolism; and between being very recognisable and very inconspicuous at that same time 
The same holds true for rings: While it can be found incorporated into a rings in a number of ways, it is far less common to find a rhombus with the sides pointing left-right to the neighbouring fingers (see picture below). (In contrast, rings with squares that have a stone set in the middle are quite common, and so is a rhombus pointing to the fingertip / knuckles; so they would be much more likely to just be intended as general fashion items.)
Thinking on this further...symbols come about through intense practice over time, through religious feelings and meditations, and religious application/practices of thoughts and ideas.
You can read about the development of "Om" on Wikipedia to see that it is a long and complex process born out of the usefulness of the symbol.
So creation of an Epicurean symbol must have an interface between feeling and usefulness.
Right now I see a usefulness of the 20th moon symbol that Eikadistes created, as this is something all Epicureans would partake in.
Also, it seems that usefulness may come first and then the more it is used the more "feeling" it has. And some may feel it is useful, and some may not feel it is useful (lol)...and so everyone can make their own symbols. 
But I like this concept that Eikadistes made some time ago... I've made it as a plain symbol without words:
I'd like to throw in one more contender; the myrtle blossom, sacred to Aphrodite/Venus.
https://toptropicals.com/pics/garden/m1/Aroma/Myrtus_communis4234_flower_.jpg
Note that this is the True or Common Myrtle, myrtus communis. Frescoes featuring this plant have been discovered at Santorini and Pompeii.
I keep leaning toward a field of random dots representing particles. Maybe this could be incorporated into the moon symbol, either on the dark or the light side.
I like the simplicity of the moon symbol, however it's similarity to the crescent and star might be confusing for some and offensive to others.
It is not much of a connection, but Lucius Lucretius Trio was an older contemporary (and presumably relative) of our Lucretius, and the crescent moon shows up on some of his coins.
