Thanks for creating the library and making it Due compatible!
About the Due: it has so much RAM, you can easily store a full 128x128 bitmap in an array, stored in RAM. Here's the code:
and here's an example of a photo being displayed:
To create the code for the 3-bytes-for-2-pixels array I wrote this little script:
Ideally, the image would be loaded from some kind of non-volatile memory, like the ROM but since the ROM is completely erased on a Due for each upload this is not really a solution for me.