CC - Creative Commons, if wholly your own original work otherwise if an existing commercial product/item then definitly seek the manufacturer's permission or copyright holder.
Oh dude, that turret is awesome and I love the sword "evolution" - I always like seeing item progression like that. Oh, and not a crit...but can't unsee!
Yes, don't be rude. Anyone helping you will be volunteering their time. In the mean time, I know there was some info on texturing in the ongoing TF2 items thread.