Creating a desert in Bryce is more difficult because you can't rely on your water to make your scene look cool. We like to work with camera angles, haze, sun/sky settings, and textures to make my scenes really pop. Experiment and have fun!
The River Valley is one of my favorite Bryce landscapes for two reasons:
1.) It amazes me how much you can do with a simple mountain.
2.) Simple changes (like the angle, textures, and sky) make a huge difference in how it looks.
The Forest is another quick and easy landscape using a "mountain" to create a simple model -- in this case, a forest full of trees. Experiment with different textures (trunk, terrain, etc.) to get...
There are times when you need to place an object in Outer Space. It's not as straightforward as you might think, but it's possible and fairly easy. Add stars, comments, a moon, etc.