The license plate protector/surround is a good addition. I know my plate takes a beating in the stock location behind the left rear tire. The drain covers look perfect too!
I like the plate idea. Mine gets beat up just pulling the cover over it. The little "personal touches" are what make this your Jeep.
Your welds will work fine. Remember, many a nasty weld has been "prettied up" with an angle grinder. On tin, the gas flux will do fine. Just heed what gmwillys and Catlewis are telling you about spot welding and spacing of the spots to keep it from warping.
Magnets are invaluable for holding metal parts accurately for welding. It's that third hand you sometimes wish you had. I use everything from the fancy angled Lincoln magnets for joining metal at various angles to magnets harvested from old speakers and electric motors. Find a magnet, stick it to the underside of your welding cart and I guarantee somewhere in the future you'll be thanking yourself for keeping it.
I love those angle magnets for welding. You are right Catlewis, a couple of big magnets are invaluable when welding. It sounds like you do your share of welding Catlewis!
I thought of building the plate surround after some offroading last summer. i was blazing trails cutting though tall brush. and after an afternoon of trailriding the plate was bent. So i figured i had to do something to prevent that. My brother has a couple triangle welding magnets i use. And i have some magnats off of blown out speakers as well. I like that one you have TJ, Might need to look into those. My Grandpa told me a trick to clamp a chunk of flattened copper pipe below any soft spots to prevent blow-through. kind of the same concept. I'll definetely go slow when welding on the body. Just do a spot weld, let it cool, then do another.
I use a lot of different sized vise and C clamps, some magnets, but also like Cleco fasteners, (for lap joints) and butt clamps. A good chunk of copper is great to have too. The second photo is one of the pieces that I use for larger panels.