Price out improving the basic architectural detailing, ie, baseboards,
crown moulding, chair railings, and ballustrades. Unless you intend to
replace the standard options after you move in, it often is low on list
which I would argue that it should be one of the first things to
upgrade or customize. Standard baseboards are 3 to 4" and raising them
up a couple of inches will make a huge difference. Everything looks
better with a good aesthetic foundation and the end-result much more
substantial. Also get very involved in lighting upgrades. Make sure the
plans allow enough well-placed recessed lighting. The root of many
problem spaces is often not enough lighting options. Dimmers can be
easily added later, but do it now if possible - especially in Dining
Room, Kitchen, Theater/Family Room. Also try to do a little floor
planning to determine electrical outlets for computers, lighting, phone
lines. There is nothing more annoying than lengthy and visible wires
and you may find you could use some floor outlets, etc. For more
advice go to askinteriordesign.com. Good luck.