If you really love plants, don't have need of a lawn, and are limited by a small backyard, consider this small backyard idea: Skip the grass entirely. Stagger your plants for height and include walking paths so you can tend things in the center of the space. Remember: Our homes and our yards should be the best expressions of the things we love.
Horizontal space is at a premium in many of the best small backyard ideas. That's why it's good to look for shrubs and trees that max out interest as they grow up, not out. Try dwarf varieties for a small backyard, as well as more columnar evergreens (bonus—they boost wintertime interest, too).