I've been thinking about potential improvements/add-ons.  One of the things that the board lacks is an ICSP header. I could make an add-on board board with an ICSP header that can stack on top of it. A downside though is that it wouldn't work for configurations in which wires are directly soldered to the Attiny Micro board. 

I could also do various mini add-on boards that stack on the Attiny Micro which could also make it function as a development platform but the lack of an ICSP header currently makes that less viable(ICSP header add-on board idea could possibly fix that).

I could also try squeezing in 2 more 0805 size resistor pads for the 2 remaining I/O pins.

Tell me what you think in the comments!