Very nice looking indeed, and a handy convenience.
May I suggest a few safety improvements? First, please consider strapping the batteries down so they don't bounce around. It looks like a good bounce or a crash could leave them shorting out against the metal lid of the box, with predictably spectacular results.
Second, and related, it might be a good idea to put a sheet of plastic or other insulating material on the underside of the lid above the batteries to prevent the possibility of shorting out.
Third, if these are not AGM batteries, make sure you have proper ventilation for them.
It would also not be a bad idea to seal off the section where random stuff is stored from the battery section so that you don't get acid fumes collecting and corroding the stuff.