IMO we need a bit of info . 1st what do you need in way of storage like how many bottles for sure. Why do you need custom , there are 100s of beautiful wine racks to be found that are not custom. Are you having a tasting space in the wine cellar. What is your style ?

edenchild, I bet you could find fancy stuff online or in an upscale sort of store if you wanted to... but just the basic stuff a local fabric store would have would work just fine. Most fabric stores sell felt by the yard in basic primary colors, some pastels, and sometimes some prints. Get it by the yard, it comes in different widths, but common around 36 or 44 inches, sometimes wider- then you can cut it to whatever size you need it and you don't need seams or anything to finish the edges. Don't get squares or sheets of the stuff, you got too much racks to play with that. If you want, you could pick something bright to add a wee pop of color to the shelf fronts while still being functional. Red would be traditional, but light or bright colors would be nice too. Cut the felt to be barely inside the depth of the shelves, draping over the front edge is a PITA and usually looks like tacky crap. But do be sure to leave yourself with a few inches of drape on both ends over on the width of the shelves, gives you shift room for bottle movement as they get added or removed from the shelf. To do this... and use a fabric tape that's soft and not a hard ruler or metal measuring tape... measure the depth of your shelf just inside the braces, and that's final. Then lay the tape across the width of your shelf, using a bottle in each slot to make sure the "dip curve" is accounted for, and use that for your width measurement. Also... you might not be one for chardonnay since it's a white, but since you like reds... watch your cabs and pinot bottles. Some of them have a slight taper with the bottle and it's better to store them punt facing out instead of the wall if you stack your bottles on top of each other. Again, vibrations can cause a slide, and better to slide into the wall instead of onto the floor.

We do use LED bulbs, I am just concerned about the wiring into electrical box in ceiling. Am I overthinking it? Our plugs in the cellar are damp rated.

I see that one bin is designed for glasses -- that says to me that either it's a tasting room as well, or it wants to evoke that feel. So yes, more stylish than a closet (althoughn we spend plenty of time on closets here too!)... Agree that temperature control is a bigger challenge, but I think this is a neat use of a tricky under-stairs space. Maybe a little high-top table with a pair of stools where the crate currently is?