Well I went the extra mile...
Here is a sketch with a function drawBitmapFromSd(x,y,"SdPicture.bmp") that allows to draw a bitmap from a genuine monochrome bitmap on SD-Card!
So any black and white bitmap saved from MsPaint for example can be read and drawn anywhere on the screen. No need to convert the image beforehand.
Getting the data to display the bitmap is a little slow, so this isn't something to be used for fast streaming of pictures. Only a proof of concept that it can be done, and something useful to start from for anyone wanting to load a bitmap from SD
Don't hesitate to give feedback!
Cheers,
Nicolas