Hi there.
For Start/Back/Select I have them included as the modern version of the buttons. So they're not the standard back and select you'd see on older generation of controllers, although I did include the Xbox 360 variant in the xbox alternative layout (which is apart of the xbox named file or the aseprite file). I have considered updating the layouts to maybe include the older style layouts, especially the playstation section. I did leave a lot of buttons off the keyboard but mostly that's just from missing text I didn't do, you could always use one of the blank keys I provided with your own INS or DEL text.
I appreciate the comment, I will most likely add more buttons/layouts/options in the near future, maybe work on some over the weekend here.