tkInter and Pillow don't display any images in GUIs - program gives errors instead

[SomeRandomGuy]

So that would basically mean I can not use functions at all,

Nope just in your example, if you want success use guizero. tkinter is best implemented in a class.

bg_l.place()

where are you placing the image?

saving space

I actually looked into Guizero (haven't done anything in there yet), and I have to admit it looks way better. What I like the most there is that you don't have to type three lines of code to apply an image, but just one

app = App(title="guizero grid span example", width=460, height=210, layout="grid")
picture1 = Picture(app, image="std1.gif", grid=[0,0])

where "app" is the main window. A link to the website that seems to have a nice explanation: https://pythonprogramming.altervista.org/gui-zero/