Recently around the mods section i have seen a lot of 'Custom' splashes. At first i was like " WOW BRO how did you do that." And then i found and it's extremely simple. Don't download custom splashes OK? It's the most simplest thing to do ever.

Here is how to make a custom splash.
1: Hit Window R
2: %appdata%
3: .minecraft
4: bin
5: open minecraft.jar
6: go to splashes folder
7: edit a text document ( I know right? Really simple)
8: save and see it

And that is why i don't like custom splashes