I think your shading is quite well done, especially since the canvas is so small. An easy way to expand the collection, though, would be to swap out themed handles onto each type of weapon. . . you've put in the work to make unique ones, might as well make them modular (and to allow devs to make a theme set of weapons from these awesome sprites). Another way to expand it would be to create "magic" overlays for the given weapons (you only have the fire sword in the upper right corner at the moment, but there could be poison (green), ice (blue), electric (yellow), etc on every weapon). Additionally, you could create a set of different arrows. . . the tails or heads could be different, or dripping with something. Finally, it would help to have a solo arrow in the pack since devs would need that as a separate asset when firing the weapon.