I see, that's okay for now as we only have about 6-7 characters. I'm looking for a for next loop solution to generate the buttons automatically, but don't understand that dictionary shiet in python, yet and need to dig deeper in the sandbox code to know where all acting characters are stored.
The game has a couple of predefined screens as buttons like
base_button (base.rpy). You could create a new button type based on the
screen belt_screen()'s interface images, so they match with the original imagebuttons.
screen file_picker() is a good example where buttons are generated for each slot page. It also uses the
base_button graphic.
As long as they won't add Piotr together with the bro hangout events sooner, chapter 2 is the next stage of new characters to add. Someone like Cecilia is only background image stuff.