I actually use several different systems, depending on the situation. It isn’t quite as neat and consistent as I’d like, but it’s just how things developed.
For most number memorization, I rely on the Major System for numbers above 10. For 1-10, I use a rhyming system, except for 0. 0 is an egg.
I found, though, that when I went to memorize the first 100 digits of pi, I needed a different approach. I’m memorizing it in six-number groups, which equals three images per location in the memory journey I’m using. Because I needed additional help differentiating between each group of six numbers, I decided I needed a people-based PAO system. I then use those people to represent the first two-digit sequence in each six-digit block, just so I have a better idea of when I’ve moved on to a new group of numbers and also so that I have a person who can interact with the other objects in that location. For example, 067982 is Steve Jobs wearing a cape and waving a fan. Without using a person for those first two numbers, I’d have an egg, a pile of sticks, a cape and a fan. Do-able, but maybe not as memorable.
Sorry: I can’t seem to write short posts!