You should check out the morebeer site for some basic configurations to give you an idea. You of course aren't limited to these designs, but it will get you started. If can't weld, you can always bolt the frame together. If you don't like that idea, you can use wood. I've even seen people use copper pipe to make a frame.
There are an infinite number of configurations and options that you can include, to fit your specific brewing style and situation. It helps to have an idea of what options you want, before you start designing. Do you want to use multiple pumps, one pump, or gravity feed? Do you need something you can break down at the end of the day, or does it need to be movable?
The list goes on and on.