Sunset at Hamilton, Brisbane, Australia

Is a silhouette okay against a sunset, or should I have tried to get

some detail into the building and trees?

When taking sunset pictures the objects in the foreground will always be a silhouette if they are backlit, unless you use flash to make them show up, one way to may have improved the photo is to have less black on the right side of the scene, the building on the right imbalances the picture and also tends to draw the viewers eye to it instead of the nice sunset, in other words less foreground and more sky. If I may make one more suggestion: have you tried using 100 speed film and slower shutter speeds and smaller apertures using a tripod for these types of photos?

If you're gonna silhouette something against a sunset, I like to make that silhouette as interesting as possible and identifyable: a landmark, a grain silo, a famous (or at least interesting) mountain, etc. The smaller aperture will help make sure the edges of your silhouette are as sharp as possible. You also might want to try taking the picture with the sunset lighting the object. Often, the color in the sky will extend quite a ways overhead (and even into the east) which allows you to get a well lit subject with the sky as background.

The sky is beautiful on oyur picture, but the subject could be more interesting. Try to go for a single, large subject in the foreground next time.