“Custom options” includes whatever you and I can agree on that will make your guitar be as you want it to be, whether that is artistic, ergonomic, tonal, structural, having to do with special woods or materials, or some feature of design . . . but short of installing an espresso spigot on the treble side and carving an image of Elvis on the heel, that is. There’s an upcharge for those. “Custom options” include woods, size and contour of the neck, strings’ spacing at nut and bridge, fretboard width, size and shape, types of tuners, and sound (sustain, evenness, volume, warmth, overtones, and projection).
The best ornamental and design work — in rosettes and/or anything else — is painstaking and time consuming. It is also tastefully done, often with a deceptive simplicity; the best work is not cluttered.
Ornament and artistry do not make a guitar sound better or play more easily; but they do make each instrument unique, and maybe more precious. And it involves deciding how much (or little) of it to do, how big or small to make it, what colors and materials to use or not to use, where to do it (or not do it), and also compatibility in flow of line, contrast, visual texture, and proportion. These all become part of the design.