This was an idea I had recently and I'll add images in the comments when I can get time to make some designs.
Lava lamps have to have heat to run. It's a requirement. I saw a build for a wood fired hot tub and had a really stupid idea:
Use a hot water circulation system to generate the heat to make the lava flow. I don't know much about these systems, whether or not I could cast some metal pipe in concrete for a form, how to heat the water outside of an open flame (which could be cool on its own, although a candle powered lamp would be so much simpler). They're also lightless heat which has unique applications for a custom designed lamp.
A peltier unit could possibly work for heat. The other side could also provide cooling if it could be useful near the top of the design.
I'm just imaging a very long and strange lava lamp on the center of a long table that's heated with water pipes cast in cement for its base.
I would also be curious if a lamp could be constructed similar to making a custom glass fish tank.
I feel like the idea would definitely work. My concern would be the safety of the whole thing. Hot water would heat the globe significantly faster and hotter than a lightbulb. There would have to be some sort of temperature regulation mechanism to keep it from overheating.
I think you'd be right. I would definitely need to include some thermistors and some sort of 12V temperature regulation. I'm seeing a lot of 12V heating elements that could be worth testing.