making background tools with these abstract impressions is very easy. stainless steel bolts and a file or a punch, as you can see in my pic above. just round off and shape your bolt head then go to town if you do not like the impression grind it off and try again.
Then guess what people will come on here and ask where you bought it lol. I will put this out there, most of the original tool stamps are copies of handmade tools from years back. I also use tools like straight-blade screwdrivers, the edge of a half-dollar etc, just use your imagination and you can find tons of designs.