That's tough! I don't know about interesting, but have you thought about Golden pothos, sansevieria, ferns

I have been ignoring my peace lily in the basement for all winter. It is still green and alive. It can be happy in a low light situation.

Possibly Chinese Evergreen and the ZZ plant.

I find Ficus benjamina is quite happy in low light, even the variegated ones. I suppose you know about aspidistras, which seem to prefer low light or their leaves bleach out. My marantas, particularly the green one, are happier in lower light too. They do like some, though, but it can be artificial, which I presume you are able to provide. I'll have a think and see if I can come up with more.

It's interesting that lemon balm is happy in your room, I didn't even consider that it would do well indoors at all.

As a rule of thumb, even the lowest light plants require 8+ hours per day of natural light that is bright enough for you to read newsprint without eye strain. If the light is less than that, then it is only a matter of time before any plant gradually deteriorates.

If you have about that much light then you might try a Dracaena 'Janet Craig' or a Dracaena 'Lisa'. They are closely related and have deep green, naturally glossy leaves. Aglaonemas and Peace Lilies are also good choices. I don't recommend Ficus.

~Will