If you had a glass lamp with a fillable vase, what type of things would you fill it with?

Initially I thought water beads with a light.

But - given the particualr design and earthy colour of this lamp...

I'd probably use earth toned grains and layer them, (the lamp is very ractangly - so beads wouldnt suit as they're round) and maybe do this - a little miniature terrarium.
As.someone else mentioned - filling it with something heavyish would make it stable.