This is two requests in one but they are both enhancement requests concerning the same Spotlight feature.
I reckon the future Paint tool that will come to XnViewMP would include better support for Shape Selection tools (I reckon

I have made two mock-up screenshots using the Spotlight feature itself to highlight the two area changes of proposed enhancement.
1.) Shape Selection (for Spotlight) Normal -------------->this is the standard square selection
Normal (rounded) -------------->standard square selection with rounded corners
Free -------------->free-hand drawing-selection, this may be or may not be a bad idea
Circle -------------->helpful for using on rounder objects in pictures with more detail (e.g. peoples faces)
Oval
Diamond
Triangle
2.) Alpha Blending (for Spotlight)
Alpha Blending will basically add a faded 'blur' effect to the inside of drawn spotlights on pictures. I have used this feature as a default in a screen-capture editing software and it is nice. soft line-blur effect is the alpha blending
Spotlight as a tool is so useful, especially for educational purposes. I am thankful that it is in XnViewMP

This is my final request for Spotlight.