I like foilage flowers are fleeting. All the examples are all in shade, Only about an hour of sun, I have so many trees I do not get much sun. Some coleus need sun to get strong color but I have never had problems with coleus in the shade.
You are saying everything looks sad I wonder if your soil is not as good as it could be. Plus pick up some fertilizer plants in pots need fertilizer.
If you are going to the Big Box stores. Check out the houseplants. There are some really beautiful large houseplants to give you the large plant in the center of your pot.
Coleus
Caladiums
Rhoeo Tricolor
Alocasia and colocasia
I do not know your zone, If you are in a cold zone as suggested Hostas and ferns are good.
I do three season in my large pots that are out all winter . S In start with spring bulbs then the ferns come up and the lilies bloom and I add a annual petunia. The green spiller over the side I use sedum that bloom and creeping jenny.
This is a fern pot described above
Three season pot
Summer plant pots coleus tricolor Rheo etc wandering jew and Gladious is the green leaf in the middle bloom summer
This is caldium and Alocasia and colocasia
