I had a collection (maybe 10 or 12) of dolls from various countries. We purchased a different one each week at Kroger Grocery store as part of a promotion. I have no idea what the promotion was about. They came in blue square boxes, maybe with a little pink on them,but not sure, with clear cellophane windows. The dresses were layed out in a cirle under the dolls. Mine were in perfect condition in the boxes, and we sold them (gave them away) at a garage sale during a short window of time when I cared nothing about them . I have regretted it for years, and would love to find the same ones, or at least see a picture to identify them.

A custom duct cover is probably less expensive than getting an island hood to solve your problem. (The "chimney" on the hood is really a cover for a duct that the air flows through.) Because an island hood has to be finished on all 4 sides and has to support its weight from the ceiling, it normally costs more than a wall hood which normally has 3 finished sides and is supported from the wall. About the smallest price difference I've seen between the wall and island models of the same hood was $500 and it can be over $1000. The custom duct cover for our hood cost about $500. That was to get a duct cover made with trapezoidal sides because there was a sistered joist in the way of where we wanted to hang our island hood. Since it was for an island hood, that was for something strong enough to support the hood. That is a lot more weird request then getting a "flange" on a wall duct cover. A wall duct cover usually has 3 sides with just flanges at the back for screws. So what you want might be more like a small step or notch in the sides of the duct cover so that the sides are 1/4 inch deeper above the backsplash. I'd expect that to add much less than $500 to the duct cover cost. To ensure that you get exactly what you want, you should draw up a sketch with dimensions showing it. Independent, who made our duct cover, required a sketch from us before they would quote. There might be some practical problems with an island hood against a wall. If it is installed tight to the wall (so that its rear edge touches the backsplash, there might be noise from vibration since it won't be screwed to the wall like a wall hood would. If it isn't tight to the wall, it might be difficult to clean behind and some grease and steam laden air might flow behind it. If your backsplash goes behind the hood, screws will need to go through it that attach the hood to the wall.

To answer all the questions - I have regular 24 inch deep cabinets. I ordered a huge 48x96 inch piece of thin cabinet 'skin' to go on the back of my island, and the same type of 'skins' for the sides (I called it backerboard above because that's what the OP was referring to, I think). I forget exactly what they are called, but they are just a cosmetic covering for sides or backs of cabinets. My huge piece of skin for the island was damaged in shipping, so I decided to cut it in half and use it anyways - that's why I have trim down the middle under my corbel. I like the way it turned out. If I had to order my cabinets again, I would just order smaller skins for the backside to start with because they are less likely to be damaged in shipping. My overhang for seating is 13 inches. The stair balusters are ones you can buy at Home Depot. Ours were about $80 each - we decided to get the unfinished oak ones, but they do sell softer pine ones for about $50. We ended up cutting some off the top of the baluster to work with our island height, and I did add quarter round around the bottom. But that's it. We secured them to our wood floor with screws. I'm in the process of doing picture frame moulding under a chair rail in my dining room. It is fairly easy. I think the most important thing is to focus on getting the distance between/above/below frames consistent. I used a 3x5 card to mark 3" between each frame. It worked great! The frames aren't the exact same size (working around electrical outlets and different sized walls) but you really don't notice.

There are two unusual treatments I have done to the back of exposed cabinets. However, they were both situations where only the back was exposed, and the cabinets were bracketed by wall on each side. I don't know how this would look in your application. In one application we ran the flooring, in the same direction, up the exposed cabinetry. It is a very modern look because the cabinetry actually disappears a bit and the counter seems to be suspended between the walls. (There is seating there so it is also durable) In the other application we ran the same white subway tile on the back of the cabinetry that was used in the backsplash. However the back wall of the kitchen has tile to the ceiling including the window jambs and sills. The cabinetry in question parallels this. Again, there is seating there so it is durable. This was influenced by commercial kitchens and by certain types of French bistros that are tile-heavy.