Not to be condescending, but you would profit greatly from courses
in the history of art and design. I'd start with visits to every art
or design museum in your area. Also there are Art History videos
available at Khan Academy which may be of interest.
Also this book, _The Design History Reader_, seems to be an
interesting compilation of design writing through the last couple of
Designers don't generally do how-to's, as design is not the sort of
mechanical process that lends itself to step by step demonstration.
There are many books on the techniques of rendering jewelry, but
that is different than a how-to on design itself.
Occasionally a designer may publish a pattern book, Thomas
Chippendale's _The Gentleman & Cabinet-Maker's Director_ comes
immediately to mind. And several 20th century designers have
published design manifestos, most notably Le Corbusier and
Buckminster Fuller. But the only jewelry designer I know of who has a
reproducible method of design, that is, one that can be taught as a
sort of step-by-step, is Omar Torres. While he was the head designer
at Bulgari he taught his method of designing via motifs to his
students at FIT. But as Maurice Galli, head designer at Harry Winston
and professor at FIT, says, "A designer thinks with his pencil." Pick
up a pencil and draw, draw, draw.
Charles Rennie Mackintosh was an important architect and furniture
designer working in the Arts & Crafts style. Here's the Wikipedia
Murrle Bennett & Co. was a 19-20th century firm whose designs seem
primarily to be in the Aesthetic style. At least, those of which one
can find photos on the Web.