What a lovely and immaculate iris garden, Timothy!
My one separate "iris bed" (actually a subsection of a larger bed, underlaid with gopher wire) hasn't turned out that well. The irises are crowded and I need to get in there and lift/move some of them, and to be honest, that part of that bed just doesn't look good to me, out of bloom or even IN bloom. (Even though everything in there is supposedly more or less midseason, that's apparently a long time and not everything blooms at the same time. So out of 14-17 or so irises, maybe 3 tops will be in bloom at the same time. It just looks awful.)
What does seem to work for me is taking 2-3 irises and planting them near each other, out in the general garden where there are other plants nearby. I try to take care to mate iris colors pleasingly, so there are not two of the same color, and not two clashing, but with the goal that they bloom more or less the same time, or at least have a good overlap, and they look good together.
'Pinkity' and 'Bloodline' pair - accidentally mixed (I don't know if I'm going to have the energy to separate them out this summer, and I'm not sure that I should)
'Lord Jeff' and 'I I Stutter' (the taller iris behind them is 'Sweet Musette'; she is later but she overlaps the first two a bit, but she does not play well with them, so she will be removed)
'Afternoon Delight' and 'Darkside' ('Darkside' helps pick up the lavender in the falls of 'Afternoon Delight')
Now, if I had a large canvas of land (like Timothy) and were going to lay out actual beds that had ONLY iris (not likely; I'm sure I'd slip something else in there
), then I suspect that I would LIKE to try to arrange them with named themes (which might mean a series of smaller beds and things not blooming together). Things like 'Science Fiction' ('Total Recall', 'Triffid', maybe 'Purple People Eater'), 'Love and Kisses' ('Wedding Kiss', 'Passionate Kisses', 'One Last Kiss', 'Love Continues', 'Unbelievable Love'), and so on.
But apart from the whole colors, and season of bloom timing thing, one thing that I have noticed with the TBs is that some of them, well, have smaller blooms (not to mention shorter stalks), whereas others are quite tall and have huge magnificent blooms. Since the overall goal of the garden is to LOOK GOOD, and I'm not sure that smaller bloomed irises look good with the more large and robust ones, then the whole idea of themes may have to just go out the window. Keep stalk height, bloom size, bloom time, and bloom color in any one area all more or less compatible - but like Timothy, break up those colors. Two of any one color just don't look good next to each other (although a self and then a neglecta or an Emma Cook or a plicata can).