I was a personal trainer for a while, and most basic programs are designed the same way. Please note that these are BASIC guidelines!
First, you need to hit all the major muscle groups. Those are:
Abs (although these can be considered upper body)
OK, so that said, here are a few guidelines for designing strength programs:
-I've listed these in a specific order. You want to do the larger muscles before the smaller ones in a specific workout. Back is larger than biceps, so I listed them first.
-Some people do all UB one day, and LB the next, some people mix it up. Either is acceptable.
-Do abs last in your workout. There's a reason it's called your 'core'- they are used in pretty much every exercise to stabilize the motion. Doing abs first will weaken them for the rest of the workout, and may lead to injury doing another exercise.
-Try to leave at least 48 hrs between working any particular muscle group twice.
As for new exercises, just try googling "Back workout" or "bicep exercise" and you will get tons of ideas. myfit.ca has a decent database. http://www.myfit.ca/...rch.asp?muscle=Chest
Good resources are certain books, specifically "strength training anatomy" http://www.amazon.com/...lavier/dp/0736041850
or the ACE manual (which is a huge book) http://www.amazon.com/...257718244&sr=1-3
It's actually really worthwhile to consider doing a strength trainer course. It's usually a weekend or two (depending on where you live) and you will come away with so much knowledge. They are usually fairly reasonably priced, too.
You sound like you are not new to strenght workouts, and if you're on ST, then you probably have some endurance. I might suggest you try switching it up with some BOSU work (if you haven't already).
I have just finished my first tri- IMC '09!