Oscilloscope as monochrome bitmap image viewer
You will learn a WHOLE LOT by reading about how oscilloscopes work and coming up with a sketch on your own.

You might want to find a pre-assembled DAC (digital to analog converter) shield that comes with an Arduino library to make things easier as a beginner.

The schematic you show is called an R2R DAC, or resistor ladder DAC. It would work just fine in the Arduino, but two channels of that requires a decent number of pins.

Note that to do 2D images you will need another DAC to generate the other axis. If you only want to do raster images, you could design an analog ramp generator with op amps, but I suspect that may be beyond your level at this point, and code might get you there faster and keep you more focused on learning a single thing for now.