What is Acceptable
There are two primary principles a film or project must meet to be considered part of the IMDb's cannon. First, it has to be of "general public interest," which means that it cannot just be a video of you and your family on vacation. Second, it needs to have been available for public audience in some format at some time. To meet these two qualifications the project has to have been shown or made available in a few platforms. These include regular theatrical showings that were not inspired by a private premiere or party, on a television station that is a regular operation and not public access of some sort, been taken from a commercial website in a very large number such as Netflix, has been put out on video, DVD, or comparable format in commercial sale, been included in an actual retailer catalogue, had a current "person of interest" such as a celebrity attached to it, been shown in a competitive film festival that is substantial and does not accept every submission made, it is of general historic interest at this point, or it is in some kind of official archive or records database. Several of these requirements are fairly vague, so it stands to reason that most people focus on films being included into the IMDb record through theatrical release, DVD sale, or film festival display.
The IMDb will also accept a variety of projects that do not fit into the feature film mold. Beyond feature films you can also put in experimental films, short films that are not simple commercials, films released on non-theatrical platforms, video games, TV series and other television programming, documentaries, and other combinations of those.