I would like some Custom Firmware modifications that alter the way the HDR-FOX displays things on the TV
Not possible, no can do. The HDR-FOX (and HD-FOX) hardware (ie the electronics) is a "black box" - ie a mystery to us, hidden inside some very large scale integrated circuits with documentation Humax keep to themselves. We can guess the general architecture of what's inside, but not the detail. To compound the problem, the Humax software (which we can inspect) that operates the mystery hardware is also an undocumented "blob" of binary code and (essentially) also a mystery.
The consequence is that we have no access to the video and audio streams sent out on the HDMI, SCART, and RCA socket, or the graphics overlays, and cannot affect them except in very limited indirect ways (one rare example being substituting our own set of digit graphics for the screensaver clock). So, do not ask for anything that needs to present output on-screen (eg a better photo album or MP3 player, or the ability to play a currently incompatible media file type).
What has been achieved with Custom Firmware is to provide a way in to the HDR-FOX's open source operating system so that our own applications can be run alongside the Humax application. These applications have access to everything the operating system has access to - ie networking, file system, and process status. With a very few rare exceptions, everything the CF does is by manipulating the files and file system, with command and control via a web browser or command line interface over the network.
If you feel you really must have some tweak to the hardware output, please feel free to analyse how the hardware actually works and let us know (in detail) which parts of the Humax code need changing (and to what).
