If your in zone 6-9 dwarf burford holly.

So multiple dwarf budford holly?

where are you located generally, both growing zone and nearest large city? That will influence what can be grown.

From the photo, I am not sure that you have room for shrubs. How deep is the bed, front to back?

Also, rock mulch may turn out to be an issue for growing plants. i don’t know where you are, but it often holds a lot of heat, and because it doesn't break down and add organic matter to the soil over time, plants may struggle. It also can be quite difficult to weed, especially if landscape fabic was installed since weeds root into the landscape fabic, and landscape fabic is not friendly to plants because it interferes with the movement of water and nutrients into the soil. I am in the process of removing rock mulch installed by the previous owner. IME rock mulch works best in areas with little rain during the growing season so that the weed seeds that blow in cannot sprout.

In your setting as it currently stands, I would be most likely to put a series of very large pots on the gravel and plant them with bright annuals.

Planting anything inside of a rock bed is going to not work over time . . . ask me how I know. You could do big planters . . . or landscape outside of the rock bed. I have a rock bed all around my house and so does my dad. Plants do not last there. They might look good for a season or two, but they tend to peter out, they can't spread and they are subject to various stressors. The rocks absorb heat and radiate it back onto the bottom part of the plants, something few plants are adapted for. Some of the Mediterranean plants might work. Depends on your zone.

Located near the Philadelphia area. Plenty of people have the stone around the deck and surround landscape.

Rock beds are such a pain to maintain! Growing up, the previous owners of our house had put down rock mulch. Invar Invariabl, weeds would grow through and when you pulled them up, a little dirt would come with them this providing more opportunities for weeds. Falling leaves did the same and were never possible to get completely up. And then when my mother decided to get rid of the rocks, it took hours upon hours to get them all up. We used to pick them up instead up being grounded. Oh, how I hated it!I will never have a rock bed! Planters might be best.

We used to pick them up instead up being grounded. Oh, how I hated it!I

@Cecily Grace zone6, thanks for the laugh.

I’m glad you find it funny but we sure didn’t then!😄

Blue salvia is surviving in my Dad's stone bed. Phlox for two summers and a heuchera and variegated hosta. Dephiniums died, coreopsis died, and day lilies spread and became a real pain. Yew survives. Junipers survive. Arborvitae survives on the shady side. Sargent crab is a good choice, I see them in the hot parking lot stone beds on some commercial sites.

Something very hardy and tough. Go ask at a garden center (NOT a big box store). You might find something that will survive there in the radiated heat and direct sun without roasting.

The size of the bed from front-to-back looks like an issue. Is it at least 4’? Shrubs get big.

One more thought - which side of the house is this? North or east side would be a bit easier on plants.

Two other shrubs I see all over the place in stone beds are the small spireas like "Magic Carpet" and the dwarf "Wine and Roses" weigela and the smaller "Spilled Wine." And day lilies like "Stella D'Oro." Also some kinds of ornamental grass, and since I am NOT a fan, couldn't tell you. Miscanthus is so invasive, particularly in the Philly area, I would not advise it. I spent a whole summer treating land at Valley Forge Nat'l Park inundated by miscanthus. There are also the "Knockout" roses that I grew next to a hot stone wall. They struggled but survived and looked great when in bloom. Not with stone mulch in that case though. That's tough because the heat reflects up all over the whole plant area. We have one rose bush in our stone mulch, I had to hack out a large bed around it NOT of stone, that part mulched. Otherwise most rose bushes will be toast eventually. Yeah, everything on stone mulch looks great upon install, bearing in mind those plants were grown to size and health in a nursery and bombarded with fertilizer, which gives them showy but weak structures. So time will tell on the plants. The ones I've mentioned are ones I see over and over on my trips to visit my Dad's condo over the years. All the homes there have stone mulch. People do amazing things with annuals in pots though . . .