I genuinely think there's an opportunity for someone (yourself, or someone else) to turn this into a genuinely social experience, a modern museum platform.
I'd love to see people's avatars walking around in some suitably tasteful way, with general info on location/age/sex/occupation. Be able to indicate if you're open to chatting.
Work with actual art historians to give prerecorded virtual tours that start every hour or something, so you can be part of a group following around.
There's something special about the museum experience, and the idea of virtualizing it in a way that makes it accessible to everyone, just through your browser rather than VR goggles, feels somehow a little bit magic.
Let people curate their own wing layouts and architecture and own art selection and where each painting gets hung. Have leaderboards of the most popular ones, and each wing can build doors that transition to other selected wings.
I genuinely think something like this could become "the" virtual museum, the same way Wikipedia is "the" electronic encyclopedia. It's just such a fundamentally different experience from how you currently browse museum's collections electronically.