Little correction, if you want every letter pair of the english alphabet you need 26x26 images, which is 676.
Foreign alphabets might need even more. For the Khmer alphabet you already would need 74x74=5476 images
To me it has always been not worth the effort. Sure it might be nice to remember the spelling when memorizing new words, but it is not worth the energy to me. Especially medical terms, which often are a combination of existing words.
Lets take an easy one: Musculi Intercostales Externi.
I do NOT want to do that with an AA-ZZ system, I want to understand what it means because that is how the terminology is designed. It is the outer muscles found between the ribs. That way I can recreate the term.
For things like brand names of medication, it can be useful, but I prefer one of the many other methods