This is a stretch, and would likely be difficult to implement, but by no means impossible. I think it needs to be mentioned in detail as a matter of the record on this wishlist.
As an astrophotographer (I don't feel privileged enough to call myself an astronomer, using all of this automation for images, like I do), my personal goal is to capture the sky, and edit the images to my liking, forever preserving my project(s) and the memories of the obstacles, work, and time spent it took to achieve them.
I've found some programs which allow one to overlay their own images, but they are far from intuitive, and they aren't programs which I would use to control my setup. Maybe this is doable in Kstars already, but it certainly isn't straightforward.
What I envision is an addition to KStars that allows the program to look to a folder which contains 1) a finished image which will be overlayed, in TIFF or jpg or whichever format is most applicable, and if necessary, 2) a corresponding FITS image of the same field which allows KStars to assign the correct position of the image and align it as perfectly as possible against the planetarium (I've noticed that with DSS overlay, there is often stars slightly mismatched.
Naturally, this would be a project to write, but could likely be fashioned using existing code which is currently used to implement DSS overlay and the like.
To me, this option would be useful because I could look at KStars and decide, without hesitation, what non-overlayed portion of the sky I wanted to image tonight, or even what portion I though might need more exposure.
I think, also, that such a function- when easily handled by the average user- would set KStars apart even further from other planetarium softwares. I think others would quickly work to implement their own overlay functions as a results of seeing just how awesome it is in KStars. Even if I wasn't using KStars, a function that allowed me to overlay my own images in a simple manner would cause me to download KStars and give it a try myself.
I'm going to feel somewhat embarrassed if this topic has been brought up before, or is already achievable with a little know-how, but I couldn't find much by searching and, like I said, I think it needs mentioning.
General thoughts? How would you make use of this function, if at all?
Losmandy G11, Gemini II, 10" f/3.8 Newt (Ostahowski Optics),
TV Paracorr-2, 2" Starlight FT, HSM20, Pegasus UPBv2,
ASI1600MM Pro, ASI174MM Mini, ZWO LRGB, EFW, & OAG,
StellarMate on RPi3 and/or Astroberry on RPi4
KStars 3.4.1 Build 2020-02-24T07:38:50Z on Win10 (updated 20200506)