I just beat the game with a Dark Elf Thief who had a great run. After leaving the chain I checked my scoresheet and looked at the artifact spawn list to see what I missed. I missed three artifacts: whip of the vampire snake, chain mail of the martyred crusader, and hornet's sting. These artifacts all have something in common. Per the ADOM wiki:

Hornet's Stinger "appears as a rapier when unidentified, making it indistinguishable from normal iron rapiers."

The chain mail "appears as a chain mail when unidentified, making it indistinguishable from normal iron chain mail."

Whip of the vampire snake "appears as a whip when unidentified, making it indistinguishable from normal whips."

Compare that to skullcrusher, for example, which dropped for me in the earth temple. It dropped as a runed-covered club so I instantly knew what I had. No risk of missing it. All artifacts should be like that.

The current system is not only arbitrary: some artifacts can be readily identified just by looking at them like robes of resistance, ring of immunity, executor, etc, and some artifacts are indistinguishable from normal useless items. Even worse, it encourages tedious behavior. I cleared 3 greater vaults in my run. I fought monsters at chokepoints, the ideal strategy, so there were piles and piles of loot on a single tile. The current system where some artifacts aren't obviously artifacts means that optimal play is to pick up everything just in case. 99% of the time it's junk and you have to waste time dropping it again, but if you don't pick everything up you might miss that one time where that 15s whip is an amazing artifact. That is the sort of tedious gameplay that ADOM has been moving away from, and when you look at a scoresheet after the fact and see that you missed an artifact it's a bummer.

So, TLDR: change the unidentified appearance of any artifact that is currently not clearly an artifact at first glance. This can be done by giving them titles like "writhing whip" or "gleaming rapier," or giving them highly unusual weights. I prefer the former, but even the latter is better than the status quo. No one is going to leave a 14s whip lying there.