Let's say you want an inexpensive structure so maybe do something like concrete blocks. I know what you are thinking, they are just plain. But if you do it in a different way you can make it work.
Here this pergola is built with concrete blocks that protrude out. This is two blocks wide and we have one that comes out halfway and we have half block behind it. Then the greatest thing you can do is you just take what we call gutter screen which you can buy in about three to four foot strips. You cut it in sections that fit on the inside of each block. That is what holds you dirt and your plant material, that type of thing.
Then you can go ahead and plant anything you like. Here we did a whole assortment of some tropical plants, like the pitcher plant which will survive in the summer time all the way until you have a hard frost.
Bromeliads, ferns and of course you can also do Perennials things like Ferns, English Ivy, Sedums, types of ground covers, that type of thing. Remember though, if you are facing the west or the south it's very hot so you want to do heat tolerant types of plants.
I think this structure does better with semi-shade. Now you can do columns and form this Pergola which has a planter box on top or you can go ahead and build just a retainer wall. All of these holes - all these little cubby holes - are filled with gutter screen. That's why the plants don't fall out from the bottom.
Now you have a planted wall that is totally different from everybody else in your neighborhood - and it can work with a traditional home - or with a contemporary home of course. Great idea!