Please add some screenshots

I think he meant to add some screenshots to the Test Plan section of this patch so people can see the new icons without having to apply it. :)

Much better. Now the margins need to be 4px rather than 3px. If you haven't already, make sure you read the HIG section on icons and the workflow tips wiki page it links to.
https://hig.kde.org/style/icons/index.html
https://community.kde.org/Guidelines_and_HOWTOs/Icon_Workflow_Tips

I'm not going to be picky about diagonal lines in this case, but just be aware of the technique for making pixel perfect 45 degree lines in the workflow tips page.

In the KTrip icon, the overhead cable and the horizontal line connecting the tram to the cable are out of alignment with the pixel grid. Any strokes should be converted to paths (sometimes SVG renderers make strokes look jagged).

I think the air plane in the KDE Itinerary icon is too small. It would probably be a good idea to enlarge the plane and cut off any parts outside of the icon, similar to the KTrip icon.

It may or may not be good to remove the blue background objects. They add a bit of flavor, but they're also a source of complexity that doesn't really enhance the meaningfulness of the icon.

These are lovely icons, BTW. Very nice work.

Awesome work indeed, thanks! I've integrated that in the app, now trying to find all remaining uses of the old one elsewhere.

thank you :D