The Ethnologue (http://www.ethnologue.com/) is a comprehensive reference (available both in print and online) that is meant to include representation of as many known living languages around the world as possible. Linguists and other researchers interested in languages often cite the Ethnologue when providing statistical/demographic/typological information about particular languages and/or language families. SLLS recognises that information in the Ethnologue about sign languages in particular should be as complete and accurate as possible, to avoid misunderstandings by the many researchers who use the Ethnologue as a definitive language documentation resource.
If the sign language(s) you work on are not represented in the Ethnologue, suggest those sign language(s) as new entries in the Ethnologue database, providing as much information as possible. In some cases, it may be that very little information is available, but anything is better than nothing.
If the Ethnologue already contains information about the sign language(s) that you work on, but that information is out of date, contact the Ethnologue to provide more up-to-date information.
Albert Bickford of SIL is available to help you with submitting a change request, should you need any help or advise.
You may want to check whether SIL, the organisation publishing the Ethnologue website and book, has published a survey document about the sign language you work on, and see how that relates to your own information. There have been many regional and country reports in recent years, for example on sign varieties in India [PDF], Taiwan [PDF], Nepal [PDF], and Haiti [PDF], to name just a few random reports. See SIL Electronic Survey Reports to search for sign language or specific countries.