Yes, there is room for annual flowers/plants in the lawn of perennial flowers/plants! We choose to use containers for annuals.
Last year I planted “Wave” petunias in the old containers. These hang like photos on a wall in an indoor room by decorating the fence “wall”. Cost = $3 each. I planted lantana and verbena this year….”Citrus” and “Raspberry” photos below.
Wave petunias
The next project was filling hanging baskets. These have another variety of “Wave” petunias. We did three more baskets with begonias. Cost = $5 each (including new cocoa fiber liners).
Hanging baskets
Three pairs of foam containers flank the front porch step. My tradition/habit is to have geraniums and spike plant (foliage). I choose variegated Salvia for the largest of the containers. Cost = $4 each.
Front step containers
Last but not least is a pair of containers for purple fountain grass by the garage doors. This terra-cotta looking container has weathered well over 10+ years (unlike the real thing). Cost = $8 each.
Purple fountain grass
Container contents Total = $74 plus some potting soil and mulch to top off.
Raspberry Verbena
Citrus Lantana
elfcroft 
My favorite grass is purple fountain grass. The seed heads seem to catch even the slightest of breezes. Alas, they won’t survive our winters and I rarely plant anything that can’t stand up on its own.