Well, that was certainly enough pics on sunsets. Now that we what one is, haha {A bit of sarcasm there}
Some of them are quite do-able in Bryce, others are well dependent on your skill set. And finally others are just plain easier to do in another app.
I guess it depends on where you are skill wise and time wise. On what your going to accomplish.
As for having a low sun that is visible, Control + Alt click on the icon at top of screen that looks like a sun and while buttons are held down click where you want it to appear in your scene.
Buildings are just basic blocks at it primitive level, so play around and see what you can create. Take advantage of combining the cubes using booleans.
If you don’t have the lastest version of Bryce get it, instancing will help with the vegetation.
Most of all have fun and when you do get stuck, post a screen shot and someone will help.
