2,7 and 8, 15 and 19 are all 256 x 256. However, they do not follow the same differing pattern.

For “2” and “8” it’s just a matter of flipping every other 32 pixel column.

For “7”…it’s a little tricky. First you need to flip every 64 pixel column, and then flip every 32 row.

I’m guessing that since “7” is the background of the eye, it has a different rule than the “foreground” of it.

EDIT: “15” follows a 64 column rule, that needs to be flipped.

“19” needs to have every 32 column flipped, and then every 32 row flipped.

1 - overall, flip every 32 column 512 x 512

2 - button, flip every 32 column 256 x 256

4 - face, flip every 32 row 512 x 512

6 - face, flip every 32 row 512 x 512

7 - eye, flip every 64 column, 32 row 256 x 256

8 - pupil, flip every 32 row 256 x 256

15 - hand , flip every 64 column 256 x 256

16 - cap L, flip every 32 column 256 x 256

17 - hat base? . flip every 64 column, 32 row 512 x 512

19 - eye base?, flip every 32 column, 32 row 256 x 256

I think it has to do with the order the game “draws” each item. It seems that the earlier something will get drawn, the more complicated it is. Can’t really tell for sure though.