2-d animation set design.

Here's how we do it:

The storyboard artist and the director discuss the various rooms in the animation, figuring out their size and location. The storyboard artist does some research into the style of the period -- in our case, roughly 1950's America -- and uses that to suggest objects. The storyboard artist then draws up the rooms as part of the storyboards, and the director changes things as necessary.

I'm a little confused at your needs, then. Here's the process I outlined:

1. Draw an overhead view of the place in which your animation takes place. That will tell you where everything is.
2. Draw storyboards based on that overhead view. If the storyboard looks wrong, compare it to the original overhead view. Adjust one or the other.

Have you tried applying this process? What part of this process is giving you problems?

I've been working out a "back yard" solution, piecing stuff together in a way that serves my needs:

I've found an easy (and free) 3D program called Anim8or that I've built a few sets in, either for animated background or still backgrounds, then rendered that out with flat colors, further flattening it out by vectorizing it in Flash either as a still or an image sequence. This allows me to model out the set and use it over and over.

I'd like to be using watercolor backgrounds, but I'm not so good with that yet (or not so confident). I may eventually mix it up.

But with regard to set design, I will often sketch it out. Even if I was still doing a watercolor of it, working it out in 3D helps me visualize the place better.