Here are some options, depending on the context:
Formal:
* Collection (most common and neutral)
* Assemblage (implies a curated or organized group)
* Repository (emphasizes storage or preservation)
* Archive (specifically for historical or cultural artifacts)
Informal:
* Treasure trove (suggests a valuable or significant group)
* Hoard (implies a large or hidden collection)
* Cache (suggests a hidden or secret collection)
The best collective noun will depend on the specific type of artifacts and the way you want to present them.