I'd been meaning to build gas bottle storage for the welder for a long time. It matters that the bottles don't tip over: the contents are under very high pressure, and if the stem breaks off, it could become a projectile.
The brackets that hold the bottles are made in part from the crappy old Harbor Freight welding cart I used to have. Two bottles stand upright, chained to the side of the cabinet that holds the TIG welder.