I wish it was an easter egg! I'm still learning my way around Assembly, and that was genuinely the best win screen I could think of at the time. One thing worth noting about IFJMP and JMP - they will immediately run whatever they jump to, essentially meaning they take no clock cycles. Realistic? Probably not. But an important quality of life feature? Definitely. At the low speeds the TC-06 runs at, every IFJMP requiring a full clock cycle just to get to whatever it's supposed to run would have a drastic performance impact.
As for image format sizing, honestly, I'd just say to have a giggle about it. Everyone does goofy stuff when they're still learning their way around computers - I know I did! Took an embarrassingly long time for me to learn that file formats are more than their extension - I got started with modding Morrowind waaaaay back in the day, and I, on several occasions, tried to make "models" by renaming various image files and such. Wasn't till a bit later that I found Blender and got started actually modeling.
On modded peripherals? I'd love to. Adding new 3d ones might be harder, but I think it'd be doable. I KNOW I want to ship a functioning network peripheral (or several) for use in the base game, and then work on making some kind of internet system go with it (like TCP/IP) - making the grand finale of the built-in levels be an actual hacking mission or something would be super cool. Given my noobness at Assembly, I have a feeling it wouldn't be that hard to break, even for the average player. As a bonus, with actual over-the-internet support for the network peripheral, you could even engage in hacking battles with other players, which would probably be tons of fun.