First, awesome tool , this was what I was looking for.
The only issue that I had is actually for bigger resolution works, shapes and the capacity of change the pencil size are really necessary.
The ui is awesome, simple and easy to understand,
Thank you! This is so cool! :D I made a GitHub issue for your request: https://github.com/fabioarnold/MiniPixel/issues/32
For now you can try holding shift to draw lines and alternate between pen und bucket by pressing N and B if that is any help to speed things up... I understand having different brushes will be really helpful when sketching or working on large pieces.
Looking forward to seeing your work! :)