This firmware supports a user created bootup logo. By default there is not one included in the firmware, as this means that once flashed they generally stay.
The Python script converts an image passed into it on the command line to a .hex file or a .dfu to be uploaded to the iron in DFU mode (similar to the process described above). The image can be in color and any size, but it will be resized and converted to 1-bit color. However, it looks best if you create a 96x16 image in an image editor and color the pixels black or white manually.
There are community logo's already converted available for download in the releases in IronOS-Meta.
The converter requires at least Python 3 and Pillow (if you don't have it, it will tell you to install PIL, which is an old version of the same thing). See this page on StackOverflow about installing it.
What works can vary, but this command may work:
python3 -m pip install pillow
Then, to convert an image:
python3 img2logo.py infile.png out -mfor Miniwarepython3 img2logo.py infile.png out -pfor Pinecil
Run python3 img2logo.py --help to see available options.
Upload the HEX file to the iron in DFU mode and, if the file's extension changes to .RDY, your custom splash screen should show up on startup. You perform this the same way as if you were flashing a new firmware, and all of the existing notes around this apply.
If you have flashed the IronOS-dfu alternative bootloader, you should use the .dfu files instead
For Pinecil, we require using dfu-util instead to flash the logo art (Pinecil does not use hex). Please see the Meta repo for the tooling for converting logo's as well as automatically generated logo's
dfu-util -D logo_file.dfu