This is exactly what I wanted, no unsightly supports, no visible uprights and no shelf supports interrupting the placement of BB's. I decided to display the shallow (measured front to back/depth) BB's on one wall with the BB's with a greater depth on another wall to maximise the available footprint of every shelf while taking up the least space in the room.
What I found in UK is that most (at least, all I could find) pre-made 'floating' shelves were only supported by a couple of bolts into the wall while the shelves were in the region of 10"/225mm deep. This may be fine for bulky lightweight stuff on shelves but I didn't want to risk heavy BB's on these (for the most part way too deep) shelves so I used right-angled brackets (with no bracing piece) to make sure there was nothing to get in the way of side-by-side BB displays.
The one thing I did out of due consideration for my BB's was go seriously overboard on the amount of brackets I'm using as the wall is made with some kind of reconstituted-grey-ash-block-stuff AND, with no bracing strut on my chosen brackets, more brackets will be required. As the brackets will be hidden by BB's anyway, I'm using two, three or even four times the amount of brackets that would normally be required. I bought them at trade prices from a wholesaler to keep the costs down but the real downside is all the drilling for the screws & plugs that's needed. It's not something I'm used to but I'm getting there, pics will follow in due course.
Good luck.