I've read a number of web pages on this one, but I'm still unsure of how to use "napkin" vs "serviette." I realize the connotations of the words are the opposite of what I'd expect as an American, but I'm nervous getting anywhere near issues of class in British society (even when the characters are aliens and nothing takes place in England!).

The question is what to call a cloth item of this type. This thread suggests that "napkin" is normal for that context -- would it be normal/expected? If there were no modifier and I used "napkin," would you assume it was cloth or that I was using language badly? Would "cloth napkin" help, or be even weirder? Please enlighten me!