Consonant Vowel Consonant (and Beyond)
I got thinking about learning 3 letter combinations: AAA-ZZZ; but then I thought that what people most want are consonant vowel consonant 3 letter combinations since so many words start with that pattern. Eg. CON for 'concentrate', 'continue' but CNO or NCO would be less useful a 3 letter combination to know as a memory image.
But then I thought that, when I attempt shorthand, I sometimes remove vowels from a word and wrute a few consonants as a quick way to write a word. Eg. WRT rather than 'WRiTe'; or CNC as a prompt for 'CoNCentrate'.
So a system for memorising 3 characters, in general, would be useful; but it would be huge.
I ended up tending to give the 1000 cartoon men and women three letter first names; that way, in a lot of situations, a three letter spelling can be represented by one image. If a three letter combination is not in those systems then you need another approach.
eg. Having a system of AA-ZZ images; and adding an A-Z image just after the AA-ZZ image. Eg. CBA would be "CB" image followed by "A" image.