I may be the only bicycle owner in the world who feels this way, but I think of water bottle cages as utilitarian items on my bike that I don't want to emphasize, (sort of like light switches in my home). I tend to go for bottle cages that match, or fade into, my bike so that the focus stays on the bike's architectural lines.
When it comes to saddle bags, if I like the way my saddle coordinates with my bike, I'll put an unobtrusive, black bag on it. If I'm not so thrilled with the way the saddle looks, I'll use a saddle bag with a fun color or print to distract from the ugly saddle.
Just one person's approach to "decorating" a bicycle
LORI
Pivot Mach 4 / WTB
Updated Vintage Terry Symmetry / Bontrager InForm RL WSD