I was not really expecting you to create all those files.
Just start with original 24-bit logo2_24.bmp.
Make 8-bit, 4-bit, 1-bit images on the PC.
Observe the appearance on the PC.
Choose the two "best". Save in 24-bit BMP. Copy to your SD card.
Then observe the appearance on the TFT.
4-bit (16-color) looks perfect.
But 1-bit (2-color) does not look too bad.
I am amazed by how good a 16-color palette works even with some colour photos.
And how good a 4-bit Grayscale (16 shades) looks on a TFT or OLED.
David.