Step 4: Continue to add details
There are plenty of chestburster images to be found online for reference, but there's nothing stopping you from giving it an entirely new style. I chose to give my chestburster arms, but you don't have to. In case you're worried about deviating from the Alien canon, the chestburster in the original film was armless but the ones in Aliens did have arms, so take your pick. The arms were very fiddly to make, but I think they give my Alien a touch more personality. They also allow him to wear a wristwatch or carry a small cane.
Remember that not all of the very fine detail will be captured in the final product. Mine looks a little bit furry in some of these photos, but it became a lot smoother by the time I'd cast it in latex.