What would be suitable?

Hi, and welcome. I suppose it all depends on what you like. For example a lot of shared lawned areas near me are divided by neatly clipped dwarf conifers, some by small fences and others with a mixture of plants. For example mine and my neighbours(not lawned btw) has perovskia, bluebells, and logs ect. We fill the gaps with eyonimsomething(hopefully someone will explain this one,lovely plant, but can I Spell it works for us (garden is north facing) but probably not for the manicured lawn.
Best of luck, but be aware gardening can be addictive