I would like to suggest 2 changes:
1) There is a variable for the filename generation in the output settings ("#") that adds the number of processed images. The problem with that is that if you choose to do a sub-folder processing, the counter is updated in a random order (see attached picture):

I would love a feature that allows to reset that counter for every sub-folder (let's say "%" or something like that), so that every subfolder analyzed has its own counter. The current implementation is especially useful when you only work with one folder. Even more, I've tried the use of the # counter with a single processor, and multiple processors configurations, and the result is the same (maybe just add the feature for single processor in case there are problems with multi-threading?).
2) The main page (https://www.xnview.com/en/xnconvert ) features an old Linux screenshot. It really looks awful. If the front-end developers could please spare some time, effort, and update that image it would be nice for us Linux users (maybe too update the Windows and Mac images too?).
Thanks in advance, I just discovered this program and it's really useful.