If attention to design and style are a must, then a digital signature is perhaps the best available option, despite not being the preferred one by you.
If the purpose is to add a personal touch to your prints, then I would suggest as others have, to practice your signature, find something you feel comfortable with and yet expresses what you are trying to convey (such as penning your name by hand on a limited edition print). Practice writing your last name just as you would do it once the prints are ready (type of paper, sharpie or fountain pen or brush, etc). Not everyone has great signatures, but what your prints are is great photos. The signature makes it one of a kind.
Lastly, I think it's worth studying how others have signed their work. A simple google search of artists and their signatures, shows their style, and how their work was immortalized -in part- through that hand-written name.
Hope this helps.
(Take a look at Matisse's signatures below. Same man, different entries. All him, but despite his incredible skills, they appear unique one from the other, and yet remain special).
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