Steel storage near the door where you bring it in
It would be nice if you can drive the truck/trailer in the door right next to the rack and unload without carrying very far. Better yet, have the rack accessible to a forklift or other type lift if you have one.
You'll also want your welders with gas bottles to be fairly near the door. Yeah the bottles will tilt and roll across the concrete fairly easily, but it'll be easier if you don't have to move them very far.
It's also nice to be able to run the stick machine's leads out the door to work on large stuff (barn trusses, farm equipment, etc). You may or may not do this sort of work.
I'd put a table for tig work in the back. Most of the tig stuff I'd do is small enough to be easily hand carried. With the tig in the back you might be able to leave the doors open and not get too much wind. Your tig and stick may be the same machine. In that case I'd put it in the back and buy more lead. You can also semi-permanently install lead from the machine to some quick-connectors near the door.
With mig there's a limit on the length of the gun and still have it feed the wire properly. I'd probably keep the mig machine on a roll around cart so you can move it to the work. If you have a machine with the separate feeder, I might consider building an overhead boom for the feeder.
Grinders/sanders can be put in the back of the shop. I'd try to keep these away from welders and other sensitive equipment so you don't get grit in everything.
I'd put the bulk of the tools on the cold side of the shop. The hot side would have a few tools: grinders, hammers, clamps, vice-grips, 1-1/8 wrench for regulators, etc.
I'm sure I can spout off a crapload of random ideas. Let me know if you want more
