the first couple (simple) options for BBB boot customization

before getting into building one's own images, i just want to
clarify the first couple easy possibilities for BBB customization to
make sure i'm not missing anything.

  once you've flashed one of the images and boot, i see two fairly
straightforward customizations:

* in the FAT partition, modify the contents of uEnv.txt
* in the Linux partition, build and install a new /boot/am335x-boneblack.dtb

  without going any further, are those the basic possibilities? am i
overlooking something obvious in terms of customizing the *boot*
process? (and, of course, there's just installing a new kernel as

  more shortly ...