We used to do a lot of stuff with making our own boot sector. We produced a cool template that not just fit in 512 bytes but could function as a com program as well as write itself to the boot sector, without costing any extra space that you didn't have to fill up anyway.

Checkout bmagic1b.zip which can still be found various places. Some of the boot sectors worked by low level vga hacking, so have started not working as technology has changed - but still, most of them do still work.