How much sun does this area get? How big is the planting bed? Do you want season long color? what color, evergreen, short, tall, shrub, perennial, annual, variety of plants or just 1 or 2? FWIW I have a bridal wreath spirea in the south west corner of my house that is in a partly shady spot so I have part shade plants nearby (Brunnera, creeping phlox, tulips, hostas, siberean iris)

With the exception of the hydrangeas, all of those are full sun plants and a bit on the droughty side as well. Once the trees grow and fill in more - and that often happens faster than you expect - they will be casting their own shade and those plants will not be very happy. And you do not want to plant something now that will have to be dug up and moved later, disturbing the maple roots when you do. And while it is a totally personal observation, those plants just don't reflect the character of the JM's very well. kaitain4's suggestions are much more in character and kind of the typical JM accompaniments. You could also add hellebores or epimediums to the mix as well.

I grow marigolds on the edges of my lasagna beds, but it's more of a pretty factor than a companion factor. And with this years bed rotation, the marigolds are on the edges of pepper, squash, and bean beds, and not along the tomato beds at all, lol. And I thickly direct sow marigold seed too- that way it's a nice bushy border and if/when they get bug-tacular I can just pull those plants if needed. This year it's carrots and leafy greens edging the tomato beds- but that's more of a got that little space left over I can cram them into rather than companionship. But hey, if it helps, why not? I've never been sure how basil is supposed to improve tomatoes either- I always figured it was kind of an old wives tale because tomatoes and basil are so often companioned in cooking rather than the growing aspect of it. I would never grow garlic in my tomato bed- my garlic gets it's own beds, and honestly is one of the only beds that is perfectly picked clean of anything that could compete with the garlic. Garlic might be good for tomatoes, but I wouldn't want to chance tomatoes out competing my garlic. Borage gets it's own growing space too, because it has it's own application, and I don't want it competed with. I grow calendula aside too for the same reason. My sage is in the herb garden, and I don't grow chives because I have large swaths of my lawn that are thick with wild chives so I don't need to grow any. Nasturtiums can be a great companion plant as far as I'm concerned- but as a companion plant only as a trap plant that I'm willing to sacrifice. I had a nasty aphid infestation last year, and the nasts trapped almost all of them- and when a bit of the plant got infested, I promptly cut it off and drowned it. I grew them next to peppers and squash last year, and they didn't get a single aphid. I wouldn't rely on nasts as a companion to just let sit and do whatever. But then I have the tendency to grow hedgerows of nasts because I use them a lot for various eating too, so I can use them as sacrificial companions and eating plants.

You could try its cousin, Sedum reflexum 'Blue Spruce'. Or blue fescue. Or for a different color combination, Sedum Sunsparkler 'Plum Dazzler'. Will be taller (to 16") and not evergreen but loves the same conditions.