Well, considering that the movie this came from was made in 1986, and the final "sequel" was made in 1997 I seriously doubt 20th century fox is going to get themselves in a major twist over something like this, it would hardly be worth their time to sue anyone over.

If the Aliens franchise still made huge money in merchandising (such as the Star Wars or Star Trek stuff still does) then I can see them maybe getting a bit miffed, but lets be honest, not a whole lot of people would line up outside a Toy's R' Us to get the latest "Ripley" action figure if they came out with one tommorow.  

Put a new Star Wars toy on sale and you'll be hip deep in geeks dressed like Jedi's before you can snap your fingers, but this just isn't the sort of public reaction you'd get if you'd try to market a new "Corporal Hicks" halloween costume.

So while 20th Century Fox does hold the copyright on the film and said copyright doesn't technically expire until 2081, I can't imagine that they are going to get too upset over something like this, assuming they even notice in the first place.

Now, would I personally buy this item for use in work I wanted to resell?  Probably not, even though 20th Century Fox is unlikely to get too hacked off about it I still wouldn't use something like this in a commercial project, but I could see buying it for personal use.