There is an option in KStars/Ekos preferences to use the Summary Screen Preview. In KStars choose the "Settings" menu and then choose "Confugure KStars..." and then in the Configure screen on the left click "Ekos" and choose the "Capture" tab and there is an option to activate called"Summary Screen Preview". Once this is active you should then see your current image in the Summary Screen. See the attached screen capture:
INDI/KStars on Raspberry Pi 4, 4gb
Raspbian Buster with AstroPi3 script configuration
Skywatcher HEQ5 Pro Mount
Canon 600D Camera
Orion SSAG/ASI120mm @280mm Guide Scope
Adafruit Motor Hat shield
Adafruit GPS Module
Generic Bluetooth Joystick.
Startech 7 port powered USB Hub.
Same issue, no images on summary screen. But something else happens: With DSLR Image Viewer turned off, I can't see any pictures in the guide TAB anymore! Neither previews (Capture) nor guide images (Guide) will be displayed, thus I cannot choose a guide star. With DSLR Image Viewer enabled again, the pictures return. Weird!
I'm having the same issue, thought I'm on the Raspberry Pi4 OS, but I remember the same thing was happening on the RPi3 as well. No preview Image on the Nightly Build version as well.
To be honest, I've never seen a preview image in that window so far, even if the settings are all activated. So there should be something happening here.
Did you check the FITS viewer window? When I had the issue, the Summary preview under the Capture Tab was not clicked, or the FITS viewer was not activated or I was running in Limited Resources Mode.
It is working fine for me with the stable build from April 25.
Atlas Pro AZ-EQ, ASI1600MM-Pro, ASI120MM-S, ES102ED, WO-Z61, Nikon D3300, ASI-EFW, ZWO LRGB,Ha,O3,S2 filter set
I encountered the same issue, but it worked once I saved the pictures as fits, not as native (cr2). This is kind of ok, but the file size of fits is still twice as much as cr2 for me, so I would love to have this work with cr2 instead of fits.
Also, the cr2 showed up in a separate kstars viewer, but without any controls in the viewer - so not very useful.