Based on images of his works found on the Internet, what struck me was the great variation in quality. My guess is that the inferior paintings were primarily sketches or studies, but I can't be certain.
This painting was in the National Museum in Warsaw's Gallery of Polish Painting when I visited a number of years ago. It deals with the passage in Luke 7: 11-15. It was painted in Rome, and not intended to be placed in a religious setting.
This is one of those inferior works I referred to. It is sketchily painted. Note how poorly the faces are drawn.
This is better that the previous painting, but the subject's face is still not quite right (her eyes seem too large).
If you click to enlarge this image you will find that it is quite sketchy, so I'll assume it was a study.
Painted in Rome. Given the lack of facial and other details, this too seems to be a study, though it was signed.
Another painting from Kotarbiński's time in Rome. This painting is carefully done.
Painted around the same time as the previous painting, but using a smoother style.
Another carefully done work.
Kotarbiński put a lot of imagination and work into this painting.