Something bugs me about turning on a flashlight, and standing it on its head on a piece of furniture that has a finish that could be damaged. I don't know what the risks are, but I cannot convince myself they are zero. If all you are worried about is damage from heat, then the sub-lumen levels you are talking about will probably produce negligible amounts of heat. I am less certain about damage from light.
Albert Einstein was finally awarded a Nobel prize in 1921. To us, it is still somewhat surprising that he did not win for his discovery of the theory of relativity. Neither the special nor the general theory was ever honored with a Nobel prize. Instead, the Nobel Committee selected Einstein's work in explaining the photoelectric effect. That theory overturned the wave theory of light in favor of the photon-particle theory now current in quantum mechanics.
A central result of the photoelectric effect is that the frequency (or energy) of an individual photon determines whether it is capable of interacting with molecular matter. If a given photon does not have sufficient energy, then no interaction occurs. Adding more photons won't help. Each photon must interact individually, so if one low-energy photon fails to interact, then a million similar low-energy photons will all fail to interact. More photons means more lumens. It does not mean more energy per photon.
Can the finish on wood furniture be discolored by light from a flashlight? Are the photons of visible light energetic enough to alter the chemistry of the finish? If so, then fewer lumens simply means it will take longer for that discoloration to occur. "Longer," of course, could be a very long time.
I suppose you could run an experiment, but short of that, I would probably just put my light on a stand.
