Is much maintenance required?
If it´s never used, no.
In the event of a fire, the affected head will need to be replaced.
The New Zealand Standard NZ4517:2002 requires you have two spare heads on hand for each type of head being used in the house.
You should never hang anything from, or tie anything to, a sprinkler head, but if you install concealed sprinkler heads, that won´t be an issue.
You can´t paint a sprinkler head, but the covers come in as many as 50 colours, so they´ll fit in with your interior design.
Visit www.fire.org.nz for further information on the New Zealand Fire Service