Hello, please let me know what you think and/or any ideas for this little concrete front "garden", t

Hi everyone, thanks in advance for any help or suggestions.
So i am trying to make the front of my mother's house look a bit nicer, she has been ill and hasn't been able to maintain like she used to, i will post a few pics below, i have bought some new benches for the front and me and brother will be clearing all weeds and corner bushes, re-cementing the corner parts etc in next few days.
Now i am wondering about these 2 holes, they originally had tall bushes in them but we want to get rid of that and keep them quite low maintenance, i was thinking of filling them with a layer of soil and them sort of gravel or pebbles on top to make them look a bit neater.
As you can see from pics one still has just some half plant bush monstrosity which we will pull out i think.
My question to you lovely green-fingered people is what sort of flowers or plants could i stick in there once it's full of stones or pebbles?, i'm thinking one nice big lavender or a mini fir in each of them but will this be ok for the plants? Can they just attach to the very bottom layer of soil ok, we need something that will look tidy all year round and minimum maintenance.
Here is the 2 holes with a magazine next to one of them for scale, thanks in advance guys.