Heavens yes. You can train vines up the stucco walls or espalier fruit trees against them. Even a small space can be a fine herb garden or greens/ edible flowers garden (forget about corn, winter squash or watermelon though). Think micro-greens, baby vegetables.... It can be changed from season to season because none of it (except perhaps espaliered trees) is permanent and that way you can play around with leaf textures and color combinations, flower combos, etc.

I understand what you mean by a hot house in summer. My mother has a similar yard as to what you describe. If you put in the vines suggested by greenwitch, they will help to reduce the heat and glare reflected by the block wall. You can put in a few flowering bushes to provide background height and additional shade.

I think everything will naturally tie together once the space is filled in. Flowering plants are good companions for vegetables. Roses like onions and garlic.Nasturtiums, marigolds, and Santolina help to ward off insect pests.

You can create height and visual interest by putting in a few blocks with a board across them for potted plants, or upending a large pot and placing another pot on top of it. Mulching would be a good thing, because of the heat contained in a small fenced garden.

Depending upon your location, you could probably have a pretty good winter veggie garden in your yard. Kale, collards, broccoli, mustard greens, arugula, savoy, and others, can all grow well in winter if your climate isn't too harsh.

Lorna