At a count like 2560, the thing that tends to matter as much as the art is value consistency. At 32px in an inventory slot a player reads silhouette and value, not detail, and a pack this size gets drawn across a lot of sessions, so the darkest and lightest icons drift apart over time. The ones that drift dark disappear against a dark slot, and you don't see it on the canvas you drew them on. It's worth laying the whole set on one contact sheet at actual size, over a light panel and a dark panel, and looking for the ones that vanish.
The category split you listed already solves most of the finding problem. Though 384 armour icons is still a lot to scan, so I'm curious whether the filenames carry anything past the category, like tier or material.