Actually, I don't think submitting new titles to the IMDb is all that difficult. But you do of course need to come up with the basic information that they require for new submissions. The basic requirements are country of origin and year of release, some cast members and the director, and the production company OR a distributor (for example the label that released the film on VHS). Having a link to verify the film's existance is also good - for Italian films, an ANICA link will usually do the trick. If you have this information, there shouldn't be any problems in sumbitting a new title and getting it approved. Of course, the more information you have, the better, so if you can also list crew members, running times etc then it's all the better.
Anyway, I haven't had any real problems with submitting stuff. It was just recently that I submitted a couple of titles that were missing from the IMDb: SEDUZIONE CONIUGALE (1974) with Gabriele Tinti and Rosemarie Lindt, and UN UOMO DA NULLA (1977), which - just like ISTANTANEA PER UN DELITTO - features the beautiful Monica Strebel. I just made a submission for ISTANTANEA PER UN DELITTO - hopefully it will get added soon.
There's are other types of submissions that are considerably more difficult IMO. For example, Tonino Ricci's PANIC is listed as a 1976 film, even though it was actually filmed in late 1981 and passed through the censor's board in late 1982 before finally getting a theatrical release in March 1983. Most reference books list it as a 1982 film but it's downright impossible to get the IMDb to change the 1976 date. I've tried and tried and tried without success, so I've just given up on it.