Now that you have created some maps, maybe even published one or two, you feel the time has come to be more creative and spruce up the maps with new textures, actors and various constructs. The first step in following that road is to learn what the new possiblities entail.
Some topic would be:
to name just a few.
Towards that end, the WIKIs are an invaluable source of inspiration. But those are not the only resources. Many other mappers have created tutorials from which to learn.
Here I will list all resources as they apply to advanced mapping techniques.