reducing stray photons in instruments, you only want those that go through your lens array, not those bouncing off the housing.

It would be interesting to test performance of a single fibre optic thread pulled through and coated with this to see the performance output.

While not the most technology advanced use, I think this stuff could make for a great solar powered water heater.

Are the incremental improvements over regular black paint meaningful?

Very important these days. Depending on full cost of this material.

I'll lay down a guess that having a better understanding of EM spectrum absorption -- in any wavelength -- likely has all kinds of applications. Better stealth technology, improved shielding for EM emitters, and possibly improved reflectors as well.

the inside of telescopes (and other optics)

If it emits in near IR it will make a perfect conversion medium for silicon solar cells.

trolling Anish Kapoor?