I had wanted to mention this earlier, but a couple of weeks ago I made a major upgrade to the web page on the Suleviæ (first the French page, then the English one). Previously, that page contained little more than my off-the-cuff comments on the Gaulish Polytheism Community page on Facebook, repackaged and made slightly more coherent. In the new version, I’ve gone through all the inscriptions to the Sulviæ that I can get my hands on and analyzed them in considerably greater depth. For example, the new page highlights the role of certain groups of worshippers of the Suleviæ such as the the Equites Singulares Augusti: these are the Emperor’s Own Horseguard, the élite cavalry wing of the prætorian guard, who were based in Rome but retained many signs of their provincial origins (many were recruited from Gaul or the Danubian provinces). Incidentally, this same military unit helped diffuse the cult of Epona outside of Gaul, and were early adopters of the cult of Jupiter Optimus Maximus Dolichenus.
There are still aspects of the cult of the Suleviæ that the page does not explore, or does not explore in depth. There are no depictions of the Suleviæ that I’ve been able to turn up, but I’d at least like to get a photo of an altar to them eventually.
However, I stand by most of my original conclusions from the earlier version of the page. The Suleviæ provide one of the clearer examples of ‘personal religion’ from the Gaulish provinces, not unlike the Roman cults of the Lares or of individuals’ junones and genii—but the Suleviæ are plainly of Celtic origin. They are also feminine; they are associated with, though I certainly argue not identical to, the Matronæ or Mother-goddesses; yet their influence embraces both men and women, and can extend not just over personal matters but to high affairs of state. I consider them to ‘govern’ the destinies of mortals (though an alternate interpretation might perhaps relate them back to the goddesses of sovereignty famous from Insular Celtic mythology). Regardless of who your patron god might be, I suspect that everybody is under the guardianship of a Sulevia, and it can hardly hurt to contact her and do her the homage of pious gifts and prayers.