At a minimum you could include all 2-character combos? Or even just a common sub...

kthejoker2 on Aug 28, 2019 | parent | context | favorite | on: Words that do Handstands

At a minimum you could include all 2-character combos? Or even just a common subset, maybe the top 100 or those appearing in 1%+ of the OED. And MNIST itself is kind of limiting since no one was trying to write numbers "artistically".