NOBD: reminds me of another aphorism. While "everybody knows" that you are supposed to wear brown shoes with a brown suit, it's actually quite hard to do it well. Aside from black tie, brown+brown is the only suit-shoe combo where both are the same color. So you have the risk of not enough contrast (too matchy) or too much (jarring.) Very hard to get right.
Black shoes with brown suits is actaully and "advanced" move that I do sometimes.
Brown/cream suit; black shoes (and tie, and square):
Bucks are the exception. I don't know why this is or where it came from, suppose from the idea that suede is contrified and goes with tweed, and let's face it, it is substantial and hairy and does not work well with summer fabrics and colors. This was a rule I learned when I was rebuked over it a few times many years ago. I also know that I have read it but I can't remember where, maybe in Hardy Amies? I don't think it's in Flusser.
BTW, for tan bucks to be OK in summer, they have to have brick red rubber soles. White shoes are fine for summer even with a more traditional leather sole. I think I made this one up but it makes sense to me.
My whites have brick, my dirty bucks have leather soles.
re texture, you are right about not mixing tan bucks with fine, lightweight gabardines or tropical worsted, but not right about mixing them with tissue flannel, linen or fresco. (or cotton twill)
The dark brown suit and dark brown shoes are a hard match, though I don't think they are necessarily deal-breakers. Some more contrast would be preferable.
Something I noticed about your outfits: you tend to be far too tonally monotonous, like in the most recent ones posted with all the browns, or you throw together elements that violently clash. Any way to convince you to aim for a happy medium?
The colors are good here, but I would almost never wear a woven or printed silk tie with a cotton suit--maybe a repp, I guess. In this context, I'd do silk knit, linen, or cotton seersucker ties almost exclusively. I like the tie in the pic, but I'd wear it with wool suits.