All the models in BrickSpace were first built as actual Lego models. Many of those models also were decorated with stickers, which in can really add more realism to design, but are optional. Here are some examples of the actual models. For stickers there are no rules: you can cut a sticker, design or print your own, or obtain ones from other Lego sets that you own, or purchase sticker sheets from resellers on the web, like Bricklink.
In no particular order, here are some real world photos of the models that are in BrickSpace. These were all designed by 4estFeller whose microspace work can be found in this
Flickr album. The model designs in the app and photos below were used with his permission. Please do not rehost or redistribute them.
Star Racer #1
Star Racer #13 (red)
Star Racer #7
Invasion
Star Racer #2
Utopia
Thunder Parrot
Viper Vic Viper
Classic Bomber
Coastal Patrol