In case that I used 24bit color in BMP file, Sticker Generator worked like below:
It showed warning message to ask paletted bmp.
It showed incorrect preview.
It showed incorrect result file.
So I don't think that this problem came from 256 color BMP.
It showed warning message to ask paletted bmp.
It showed incorrect preview.
It showed incorrect result file.
So I don't think that this problem came from 256 color BMP.