Making it "look more expensive"? That seems foolish.
bodonnell202 is correct that some of the third-party leather bands can look quite nice.
twanj is wrong about it being
meant to be upgraded every year. It's more like a car: sure, you
could upgrade every year (and the car dealers would love you for it), but it's much more reasonable to upgrade when the accumulated benefits of newer models outweigh (to you) the cost up upgrading - I'm wearing my first-day-purchased Space Gray Series 0, and the new Series 4 is the first time I've felt a real twang of wanting to upgrade (for this year's larger screen, plus the accumulated benefits of faster CPU and waterproofing).
tl01 is on the right track - if you want it to look
more expensive, try wrapping hundred dollar bills around it. Or maybe get a silver sharpie and write "I am rich" along the black sport band. Or maybe get a heavy solid gold chain to wear on the opposite wrist. Or find someone who is selling one of those Series 0 watches milled out of actual gold. But all of those things tend to say "I am desperate for attention" more than "I am wealthy".
If you'd really rather have one of the Hermes models (they're pretty, but they don't meet the desirability vs. cost tradeoff
for me), even though you're likely past the official 14 day window, it may be worth visiting an Apple Store (with packaging and other original bits in a bag, or out in the car), and asking if it would be possible to exchange your aluminum model for the Hermes model (paying the difference, obviously). They have some leeway in such decisions, I'm told. But they may say no. If that doesn't work, you could sell yours as "barely used" and likely get back much of the cost, and put that towards the Hermes.
I have a space gray aluminum Series 0, along with one of the original black Leather Loop bands (which makes it look about as refined as an aluminum smart watch can look - it's quite nice, actually), and more of Apple's Sport Bands than I care to think about, which I swap daily to match my outfit, mood, or whim. At the moment, I'm wearing the top half of the Light Pink band and the bottom half of the Mint band, which amuses me, and delights my nieces. But I prefer people judge me on my words and actions, rather than on what watch I'm wearing, or how expensive my accessories look.