I just received my Gameduino 3 today and am keen to try it out with the BlackIce.
It fits the BlackIce quite well, and the STM32L433 should be about 8 times faster running Arduino code than the original ATmega328.
Perhaps one idea is to use the GD3 as a graphical input device to the STM32, and then have the FPGA produce some VGA to drive large screen monitor.
A couple of years ago, I took the FT810 video processor which is used on the GD3 and with resistor networks got it to drive a large screen monitor at 1024 x 768 resolution. James Bowman sugested using a 13MHz rather than 12MHz crystal to overclock the FT810 at 65MHz in order to give the increased resolution.
My only regret with the FT810 is that it will only put 2048 characters of text on a screen at a time - which limits you to 25 x 80 text screens.
Looking forward to trying it out later.