There is a problem, maybe a bug or something similar, with both of the Linux versions, that created a Segmentation Fault (Core Dump). It is a very peculiar thing: I add a new frame or clone an existing one, then I use the pencil to colour some pixels; when I need to do an entire line, I use the Shift button, but when I move my Pad (it's a portable PC) Pixelorama crashes in a Segmentation Fault (Core Dump).
I also see this Warning on the Ubuntu Terminal, but I think this is something in my PC:
WARNING: _png_warn_function: iCCP: profile 'ICC profile': 'RGB ': RGB color space not permitted on grayscale PNG
At: drivers/png/image_loader_png.cpp:71.
So, I hope this will help you to improve Pixelorama, because it is a very nice tool :)