"There are several options. You can grow annuals vines, such as morning glory and moonflower (together), for flowers from morning to night. But in winter, you'll still see the wall. You didn't say if your wall is in the sun. My suggestions are assuming it is. If not, use a climbing hydrangea or kiwi (may not be hardy where you are; check that).
I suggest planting a perennial vine such as trumpet vine (Campsis radicans) or sweeet autumn clematis. Both of these grow fast and aggressively. You can keep them in bounds with spring pruning--aggressive pruning if need be, cutting back to 12 inches tall. They'll grow out that much in one season easily.
You can also look into roses for your region. There's a great rose grower in Maine--Royall River Roses. A rose will take longer to establish. Choose one that is remontant--that means it blooms more than once per year.
Remember that if you go the perennial vine route, this first year or so you can plant the vine and also put some annuals around it, such as canna or even a tropical banana or elephant ears. They get beefy and will hide the wall. You can dig the roots and store for winter indoors somewhere (dried up). That way you could use those for a few years, if need be, 'til those vines are holding their own. Be careful if you plant a perennial vine with something like a morning glory. The annual vine could overpower the perennial vine the first year and actually slow its establishment.
Hope those ideas help! Happy gardening! Great idea, by the way, using a simple wall!"