Allow me to first utter the obligatory incantation that seems to be required to protect one from getting flamed around here: I couldn't figure out what to search for, so my google-research was fruitless. That said, I do hope that this isn't something easily solved or I'll feel silly.
In my story I am portraying an alien culture (space-alien, that is) and including illustrations. None of the languages that would be depicted in written form on structures or "sign posts" would be at all related to or resemble any terrestrial language. Merely for the sake of enriching the background, I would love to invent a simple collection of words that could plausibly represent an entire non-existent language. Unfortunately, I have the feeling that my clumsy efforts appear to be the amalgam of thrown-together syllables represented by arbitrary symbols that they are.
To have illustrations where the "signs" depicted are in English would be as painful to me as the "Happy Birthday Bilbo" banner that was regrettably displayed in The Fellowship of the Rings.
I'm not J.R.R. Tolkien, nor have I even taken a language class outside of my native English (I'll use Lister's defense, and blame it on the fact that I went to art school). Nonetheless, like Tolkien, I'd like to create a body of words in an alien language that are reasonably believable and that I can add to with some degree of consistency as I go.
Any suggestions on what I could do to compensate for my total ignorance on the subject (besides hire a master of linguistics as my consultant)?