There is a parameter that allows for adding a file description string; this will become the wiki code of the Commons page of the file that you uploaded. By the way, the best description of parameters is to be found in upload.py itself, in my opinion. It's more clear than the documentations online.
python3 pwb.py upload "path/to/some_file.png" -summary:"uploaded with pywikibot" "source code string of the file page" -ignorewarn -always -keep
So in the source code string, you can include everything that you usually find on a Commons page (in wiki syntax), like filedesc with the information template, the license-header with the license template of your choice and categories.
--Hbf878 (talk) 14:56, 21 April 2020 (UTC)