It would probably be some application of spectral imaging [0], highly dependent on what data you choose to capture based on your assumptions about how the aliens see.

Even if you have a mathematical "photo of a planet of nitrogen gas clouds", that leaves the problem of how to present it to humans, since we have no concept of what "nitrogen gas color" is supposed to be.

https://en.m.wikipedia.org/wiki/Hyperspectral_imaging

As OP said, most astronomical pictures, even in the visible, target specific wavelengths and are thus "converted" for human vision. It's also obviously the case of any picture in wavelength beyond visible light. Keep in mind that there is also massive processing to clean the pictures, not just a translation of the wavelengths