excellent looking work! might be a bit premature in bringing this up, but when you start fabricating stuff for others, make sure you have an attorney draft a usage waiver of liability, and set yourself up to sell your work under an LLC. For years I have made parts for old BMW motorcycles and though none of them were major parts (just sidestands, centerstands, etc) I still made sure that if one of my welds didn't hold and caused an injury, that no one could come after my home and more importantly my Jeep! That said, I have made a nice secondary income from my "hobby". And it certainly paid for all my welders and plasma cutters a few times over. Good luck with it- hope you make a go of it.
I do have one question, which I am pretty sure I know the answer to- you welded flat plates for the front and rear bumpers, but if you had had the steel bent 90 degrees over instead to make your tops and sides, would those edges have been substantially weaker than welded edges? Pretty sure bends would be weaker, but not sure to what degree- certainly far less welding.
BTW your welding is tight, way too good for a 'hobby'- and that was a hella nice shop you fab'd the front bumper in. Do you weld for a living?