Whist looking through the repository of our most prolific FPGA friend Juan Gonzalez - Gomez, I spotted that he has designed an educational cpu with UART - that will fit on a 1K IceStick - so very easily on a ICE40HX4K.
The Alhambra board has a lot in common with the myStorm
The design files are at his repository here
In addition - the Apollo Guidance Computer (AGC) - also in verilog
Use google translate - to translate from Spanish - where required.