Finally got around to doing this:
This is what happens when I try to use some texture packs after installing modloader:
Left is before, right is after.
Happens to all items/held stuff regardless.
It happens with Misa's :C, the John Smith Texture pack, Inspiration, GeruDoku RPG and Derivation.
And DOES NOT happen with Pixel Perfection, Wayukian, Rustica.
I've no idea why. But I do know for certain that Modloader IS causing it. There's nothing about said issue on the thread on the Minecraft forums. Or there wasn't last time I checked.
And I tried using Optifine, and it just...WELL to put it one way, the lighting derped and it looked like the water was having a rave party.