Everyone remember's that game, Super Mario 64 for the Nintendo 64. Since you can emulate it's ROM people begun modding that ROM and changed a lot of it and made their own Mod of it.
Here are pictures:

This all has been made with a Tool made by Starxxon(VL-Tone) the Tool is called:
Toad's Tool 64
Website:
http://homepage.mac.com/qubedstudios/ToadsTool64.htmIf you need a Super Mario 64 ROM then go search yourself. I'm not allowed to provide any links to ROM's. Also, if you make your own Mod's don't forgot to make a .ppf patch file.
Setup your SM64 ROM:If you found a website, downloading the ROM go to the website(look above) and search for Mario 64 ROM Extender. Download it and execute it and select your SM64 ROM. Now your ROM will be extended and can be used later with Toads Tool 64.
How to create a .ppf Patch:PPF File's are the most importantest thing. If you edited the SM64 ROM you have to create a .ppf patch that people have to apply to their own ROM. Also ppf files are legal :)
http://www.youtube.com/watch?v=WNTXzZjo_iYThere are also tool's to replace a whole level. Toad's Tool 64 is just a Level-Editor! It let's you edit all enemey's, object's etc. If you wanna replace the level(the ground, castle etc.) then you need a more advanced tool, which will be explained later.
BTW, for people that program in ASM:
http://sites.google.com/site/jamesskingdom/Home/video-game-secrets-by-james-s/super-mario-64-exposed#TOC-The-MIPS-ProcessorThis is not my blog, it's a blog by an popular SM64 Player.
How to apply a PPF Patch?
http://www.afterdawn.com/software/cd_dvd/iso_tools/ppf-o-matic.cfmIf you wanna apply a PPF patch, don't forgot that you need a extended(look above on how to extend ROM's) clean ROM:
1. Open PPF-O-Matic.
2. Go to ISO File. Click the floppy-disk symbol.
3. Click all files, and select your SM64 ROM.
4. go to PPF, click again the floppy-disk symbol
5. Select the PPF file.
6. Now press Apply. A message should appear that say's it was successful.
What Emulator's should i use?Top 2:
1. Project 64 - Best Emulator in my opinion and of million other's.
2. Nemu64 - a good emulator. But is actually made for debugging and searching the memory.
ONE IMPORTANT NOTE:
If you wanna download the SM64 ROM legally, then you need to have the SM64 Catridge in real-life. Else your downloading ROM's at your own risk!