Big Size 20P COG ST75256 Displays Interfaced with Arduino

Other Hardware Displays
2

First off. I would choose a regular HW_I2C constructor e.g.

U8G2_ST75256_JLX256128_1_HW_I2C(rotation, [reset [, clock, data]]) [page buffer, size = 256 bytes]
  1. place the Arduino properly on the breadboard
  2. use the breadboard power rails as Nature intended. i.e. +3.3V and GND.
  3. connect the Display pins to the breadboard power rails with regular wire links cut to size.
  4. i.e. all VDD to +3.3V. all VSS to 0V (GND)
  5. connect 4k7 pullups to 3.3V on pins 17, 18 (SDA, SCK)
  6. connect 15, 16, 17 together.
  7. connect 5 (LEDA) to 3.3V with 47R resistor
  8. connect 17 to A4 (SDA) on the Arduino
  9. connect 18 to A5 (SCL) on the Arduino
  10. connect 9 (RST) to 3.3V with a 10k resistor

Run the U8g2lib examples with the above constructor.

The wiring scheme is shown in your link. i.e. which pin goes to VSS, VDD, ...
Get that correct on the breadboard i.e. so we can see the wires.

You only have 4 jumper wires from Arduino to breadboard. SDA, SCL, 3.3V, GND.

Untested. I don't have your display. Please report back.

The ST75256 only has 4 grayscale levels so it can't render black and white photos.
Anyway, U8g2lib does not support grayscale.

David.