Furnature huh?
Well for couches and things it is very easy to make them too big and bulky. A way to fix this is to have the base of the couch be one brick high and 3 bricks deep. On the front part of the couch have a flat brick two deep on top of the base, and on the back of the top just put two _x1x1 bricks. For the arms of the couch just put a 2x1 on each side. This will leave you with a nice non-bulky couch that still has room to sit on. You can feel free to make the couch as wide or as skinny as you want.
Picture yes?
To make arches, use ramps. At the base have the steepest inclined ramp, and as you go up use ramp that get less and less steep. So you may start of with an 80 degree ramp, than go to a 72 degree, then you use the other two smaller ramps. If you have space in between your arch start using plates.
Ill edit later since this is a little vague, and Ill post a pic too.
