A couple of adjustable wrenches

If for anything else they are good for holding one side of nuts & bolts.
Suggestion for the inverter. Looks like your work light is 120v AC. Get one in 12vDC. LED if you can afford it. Anything you run through the inverter will use more battery power. There is an efficiency loss with inverters so a 12v light will last longer than the same 120v light run through an inverter. Of course some things are two expensive or just not worth getting in 12v so the inverter is still a good idea.
Consider getting a second battery. You can hook it up isolated from your primary battery or just have it by itself. If you drain it dead you still have one for starting.
Did I see a voltage meter in your kit? If you are running stuff off the battery with the engine off you can occasionally meter the battery. If it meters out at 12v or less you should consider starting the vehicle. Ya know with the vehicle running the meter should read close to 14v right?
Should you think you have run the battery down and want to start it make sure you run it for awhile to charge. Certainly if it shows any symptoms of a drained battery. IIRC most vehicles need to run over 5 minutes to gain back the charge lost by starting. Too many people like to get a jump or start the vehicle and then shut it immediately off. That only looses power.
Looks like you have a nice complement of tools and emergency stuff though.
Eddited to add:
Move those lights! Under the bumper is a great way to break them off on something!