I found this very vintage letter frame image in a book from 1778. The author used a pseudonym and no illustrator was credited. However, with a publication date of over 200 years ago, I think it is safe to say this letter frame is in the public domain.
It is obviously a wood cut as are all of the other illustrations from Food for the Mind. That means it is a little blurry but to me that adds to the vintage charm of the piece. This letter frame image originally included a letter and was used as a drop cap to start a paragraph. I’ve removed the letter so you can add the letter of your choice or perhaps a small picture of something. The frame has a rope-like border with floral motifs forming a garland around the frame. There’s a pair of imperfections in the rope as if someone jostled the paper when the image was being pressed onto the paper.
This image is copyright free and in the public domain anywhere that extends copyrights 70 years after death or at least 120 years after publication when the original illustrator is unknown.