I had never thought as letters, as in of the alphabet, as being very interesting for embroidery until I saw the piece worked by The smallest forest.
This piece somehow sensitised me to the beauty of letters. Before this I thought of them as a pain to stitch, keep straight and balanced. I have found such inspiration in the stitching ideas that participants have posted in the TAST challenge so far this year.
Then at about the same time I came across a lettering book posted by Agency Eureka called Speedball Textbook. Lots of different fonts and all illustrated in such a way that they could be adapted for embroidery.
On one page I found a copy of work done in the 1682 by Thomas Weston, Gent, and put it aside as a reference, thinking it might be useful in the future.
Then on BibliOdyssey I found an entry about the German scribe, Johann Hering, who's work is attributed to 1620's, both works are very similar. (The complete book can be found at Staatsbibliothek Bamberg.) There are some lovely plates here but I think that this one would make a beautiful embroidery. The words are in old German and seem to be a psalm.
I'm sure that you could use the same words in English or maybe another piece of poetry or even something that you compose yourself, about love, family or just a social comment.