I am looking for suggestions of trailing perennial all summer bloomers for high retaining wall planting. Zone 7. Would you have any suggestions?

Sun? Shade? Moisture conditions?
My mom's favorite was Creeping Phlox/Phlox subulata.

I love Phlox subulata but it blooms strongly in the spring here in my zone 7. It doesn't bloom much at all during the summer, I'm afraid.

Sounds like it might be sunny and maybe dry location? I like purple and pink trailing 'Homestead' Verbena, for one. Maybe Bidens 'Goldilocks' if you want some yellow.

Any or all of the Cranesbill geraniums would be a good choice for a high retaining wall. They have pretty foliage, and bloom off and on all summer. They come in a variety of colors from white , pale pink and magenta right through the blues to deepest purple. They make a lovely contrast of foliage for iris, too.

to ATP!
I can think of a lot of annuals, but for perennials, maybe a cascading rose such as pink Drift? I have a row of those on top of a short rock ledge and they bloom until fall. They won't hang over a tall wall more than a foot, though.
There are some prostrate lavenders and rosemaries that might work.
I'm curious to see what you end up with !

Cerastium, Snow in Summer. Delosperma.