a) Early Alien storyboard of a Nostromo explorer examining the space jockey
b) Demons tormenting St. Anthony (1520) by Niklaus Manuel Deutsch
c) This area is transformed into the explorer in the astronaut suit
d) The pale hand of St Anthony becomes the basis for face with the area around it transformed into a space helmet, while the claw of the demon's foot here becomes the left shoulder.
e) The highlights of the clawed toes becomes the gun
f) The cloud and perhaps the club as well are transformed into air turning into vapour expelled from the helmet
g) The area with this head is turned into a mass of tubing that's part of a machine
h) Ears of the hog face demon is transformed into a light coloured V shaped area, while the head of St Anthony is transformed into an oblong shape, if the comparisons could be made at all.
There might be a way to interpret the brown lines in this part of the storyboard and how it relates to features of the demon but it wouldn't be reliable, although it might look as if the claw of the demon on St Anthony's head has become the thick part of the brown on the far left of the segment below.
i) Lower part of the lower left demon becomes the space jockey's head