I would like to add lights to my "on display" castle but was wandering what the best types of lights are? Something low power and safe? Any one with expereince of using?

Something like this

from here

http://www.minifigs.net/forum/viewthread.php?tid=30683&extra=page%3D3###

I don't know if you built that amazing colloseum, but if you did; WOW!

It is hard to work out what lights are used in that but they are certainly effective and it would be great to find out the details.

I have used Christmas tree lights with success as they are cheap, run all day on batteries and the LED lights can fit into a technic hole.

Actually that builder is in Hong Kong.

To the lighting question: I haven't tried it yet, but this is the best option I have found for interior lighting without a lot of heat.

You might need several sets to light something as big as the example, though.

I use LifeLites, they're designed for Lego uses and are quite masterfully done.