Bruxinth

Does anyone know where I can find the legitimate skins used for blocks in vanilla minecraft? I am trying to use MCAnimator and GIMP to create a new block that has similar skins to an existing block, with the just the difference being that the new block will be in smaller dimensions. If I can get the original skin and modify it to fit the new block, then I'll be able to achieve a look that relates to the original block.

What I want to do will likely require me to alter and add events and eventhandlers. Is there a to do that through forge?

So I recently just started getting familiar with modding minecraft so that I could start work on of my own ideas for mod projects. One of the things I want to do is add the force of gravity to all blocks so that all blocks will fall by default (the exceptions will be construction blocks like wood planks, etc) and another will be to make liquids be more realistic by causing them to spread and pool rather than have a block infinitely generate streams of liquid out of it. The one question I have before I begin this project is will this require me to alter core minecraft classes, and if so, will that be a bad thing, i.e. cause my mod to be incompatible with other mods?