It would be a good idea, but even better if it also had two specific purposes:
1) to invite members to help identify and add to an item's provenance
2) to publish already established provenance thereby enhancing others' knowledge on sites they study.
One thing that should be guarded against is promoting collection by squirrels of items that are best left where they are.
With that in mind, there are plenty of in situ artefacts that could be recorded and added to such a gallery, provided precise locations are kept vague enough.