With a fantasy setting, everything is new. I'm throwing the reader into a new world that has a different feel and look than anything her or she is used to. Therefore I should describe some things in high enough detail.
However, I don't feel the need to right now in the first chapter, because those details aren't extremely important to the story. I feel that most readers will be able to fill in all the gaps they want if need be. Give someone a few context clues and that give him or her enough to figure out a general idea of what things look like. Why should I go into superb detail?
I know for a lot of things I will when I start writing the RPG setting, but I feel that's because a setting is a world for other GMs to borrow. If the GM wanted to fill all the gaps she would create her own world. Therefore the details are necessary. But in a story the flow can easily be bogged down by too much description. I've seen it happen before and I would rather avoid it.
I guess I'll just have to write now and see what cracks need to be filled in, if any.