You can download many of these Mods from DeviantArt.
All items are use at own risk. All files come pqcked inside a .ZIP file. You computer should already know how to extract those. Some may be packed inside a .RAR. (Definition of a .ZIP file.) Its a container that makes transferring files over the Internet convenient. It also compresses them to alleviate disk space consumption. For .RAR files you will need to have a program that extracts these them. .RARs are like .Zip files. WinRAR will extract these files for you. Once WinRAR is installed, just right click on the .RAR file and select from the menu extract to a folder of the same name as the .RAR file. Ok, step one is over. Next, go into the folder and find another folder called "DATA". This is the folder you need. Copy it. Then navigate to where the movies game is installed on your computer.
The above is the address. In this location you may find already another folder also called "DATA". You must paste the copied folder (earlier) here. Do not paste into the data folder you find there. Paste it near by. Right click to paste if you don't know how. Your computer will then ask you if you want to merge the two data folders. Say yes. Or say confirm to do this. Or whatever the agreeing response is. Your computer may then ask you more questions. Chances are there will not be an overwriting. This is usually asking to merge existing folders. Sometimes a Mod will come with the textures that are already in the game and may already be in your folders. Then your computer will ask you if you want to overwrite them. Say yes again and again until the questions stop being asked. And then the Mod is installed. The basic idea is to extract the data folder contained within the .RAR or .ZIP and merge it with the data folder of the movies game.
Be careful with some Mods you download from the Internet. If the Modder was clumsy and didn't rename a texture of (.MSH) file then they could alter existing content found in your game. But none of my Mods will do this. And sometimes there is a reason do this this intentionally. Like the "get rid of trestles" alpha texture.
There may be one or two things to keep in mind. For instance, some items are made available to the game only after the right files have been altered to accommodate them. An example is costumes. Costumes are selected in categories. So each category has an ini file to which those costumes belong to. You must enter the name of the costume under the costume category ini file for it to show up in the game. In other words, open a given category ini file, say the category_monster.ini using notepad. You will see a list of all the monster costumes. Make sure the file is viewed in full window mode. Each costume will have a tab in front of it. Several spaces away from the edge. Go to the bottom of the list, go to the very next line, hit the tab key, then enter then name of the new costume there. Click save at the top and you're good to go. I should have a category_(name of category).ini file with my costumes downloads.
Props used in scenes also have their own ini files, so that the game can select them during a scene. Each scene usable prop must be entered into those. Most mods you download from movies game fan sites will come with the appropriate files you will need. And most also come with a ReadMe file that will explain the particulars of installing that mod.
Warning: If you don't take the appropriate precautions, you can overwrite other mods you have installed or end up altering another item in the game.
This only occurs when you are not careful with what you install. A new horse prop needs a horse ini file for it to show up in scenes. But if you already have a custom horse installed then adding the new one would overwrite the old horse ini and the new horse will show up, but the old horse will not. To fix this, just add the new horse name to the old horse.ini file, and then delete the horse ini file that came with the new horse. Once you learn the ins and outs of the files that make sets, props, costumes, etc, then you will know what to look out for. It is possible to make mods that will never overwrite anything in the game. And most of them don't overwrite anything. While some mods are actually made to overwrite stuff. Yet it is possible to alter one or two things about anything you download in order to avoid overwriting anything. Be careful to overlook each download for the Movies game. Some will add things the Modder did not mention in the Readme file. All the details are mentioned in my Readme files. So be sure to always read the Readme file. Be careful.
You can go over to my Introduction To Modding Page to get an idea about how to safely alter the files in your game.