You can see above how far apart they can be spaced down a stairwell, creating a simple, uncluttered effect, whilst keeping the cost down. The same effect can be seen here...
...an image that also shows how effective they still are when not lit.
Dew used in a completely different way is shown here, where two rows are lighting a church -- the chapel at Mossley Hill, Liverpool:
More often, though, we see them used in a cluster:
and sometimes like large stars across a ceiling:
Other decorative arrangements include this, behind a reception desk:
See how versatile they are?!
They even look good on their own: