Currently, player can build:
- ways - anywhere
- stops & stations - on ways
- extension buildings - touching existing stations or extension buildings
- wayobjs, signs and signals - on ways
- depots - on ways
This list shows that it isn't possible to have eg. a signal box before station or water tower next to a depot, unless:
a) a station "crawls" to there with temporary tiles or
b) a type of item is abused for eye candy.
Logically, it follows that another class of buildings would be nice to have - without capacity, not connecting to stations, buildable anywhere.
Eyecandy you can build as public player a lot. But this request is very easy.