There are multiple interesting files bundled in the DIRECTOR firmware update tool.
The findings here are so far limited to the old version "1.77 / 2.11 (DSP PC-Tool 4.75a to 4.80c)". I didn't realize I downloaded the older one until writing this (oops). That said most of this is probably still valid, but firmware "3.00 (DSP PC-Tool 5 or higher)" is likely to have support/params for more models.
Extracing the 1.77 installer, these files look interesting:
599 Dec 19 2018 Bootloader_gfx.tcl
602 Dec 19 2018 Bootloader_gfx_aco.tcl