On the top of the windmill, a broken tire swing can be found in the final version of the game. All of them appear to be happy and are notably smiling in the photo. Peterson's house, one you can only get to by umbrella and by breaking a window, there is a family photo depicting the Neighbor, his wife, his daughter, and his son. Also in the Mod Kit it is called 'Factory Object'.

But originally before they scrapped fear factory, it was used in the fear_factory. It is unknown at the time what you are supposed to do with it if there is anything you need to do with it at all. In one of the mailboxes of the houses, you can find a package. On the plaque are some strange symbols which as of now are not decipherable and may never be. It is unknown what it is hinting towards at this time if at anything.

On the far side of the lake out of bounds is what looks to be a satellite with a golden plaque of some sort on it. In the full game, if you go near the church out of bounds in the game you can find a gravestone with a silhouette of the Neighbor's wife, Diane on it. Out of bounds in Alpha 1, there are duplicates of the player's and Neighbor's houses, both of which are used for the basement cutscene. Out of bounds in Pre-Alpha, you can find a burning house on top of a hill. This can be found in BP_Sosed (the neighbor). When you open the cue, it shows audio files of extremely vulgar language.

In the Mod Kit, you can find a part where it says Swear Sound.

Hello neighbor alpha 1 ending