One possibility is that you create a trellis in front of the wall (one foot out) on which you grow vines or espalier some type of woody plant. Vines could be something like a flowering clematis. An espalier could be a flowering shrub, like camellia. The simplest trellis could be 3 posts across which horizontal wires (like clothesline) are tightly spanned. Annual vines (morning glories or moonflower vine) could be used to quickly fill in while other, permanent vines takes hold. If you have space at the top of wall, vines could be planted at the top instead and encouraged to spill over the side. If creeping fig grows where you live, you could plant it at the base of the concrete wall and it would climb and attach itself. You would trim it like a hedge and make sure it didn't escape past the wall or get too close to the garage. (English Ivy could do the same thing, but it would be trying to sneak off in every direction. Would be OK as long as you monitor and control it regularly. One of the dwarf cultivars of ivy would be best.)

It is a nice wall. Some ivys are more maintainable than others. I have a glacier ivy on chain link that is great and does not feel like it will devour us. Algerian ivy will devour your family, I have that further back in my garden creating a secret garden effect. You have to trim it twice a season, it gets outta hand. Creeping fig and camellias as mentioned by Yardvaark would look REALLY nice (fig comes in green or variegated). Add a white iceberg rose in the middle and two white camellias flanking it to accent the neighbors white fence. Underplant the soil strip with isotoma or a campanula with purple blooms to accent the blue and grey of the siding finishes of both abodes. Or, just let your kids paint a mural!