Move up #loop to the _random values, otherwise you'll stay at one value all the time.
Edit:
Like this:
#loop
_random = random 20
_random2 = random 5
arty1 = "HEAT105" camcreate([(getpos artymark1 select 0)+_random - _random2,(getpos artymark1 select 1)+_random - _random2,(getpos artymark1 select 2)])
~1
arty2 = "HEAT105" camcreate([(getpos artymark2 select 0)+_random - _random2,(getpos artymark2 select 1)+_random - _random2,(getpos artymark2 select 2)])
~3
goto "loop"
:beat: *Gets Shot* :beat: