Quote: "Btw, I heard that 1.20 has video textures, is it true? maybe I could use those, what format do the video textures have to be in? GIFs?"
as they are video-textures they use video-container-formats (avi/mpg) and videocodecs (mpgII,indeo, huffyuv, x264 etc.... NO divx, fpsc doesnt like some versions of this).
i dont think the vidtexture is working with alpha-channels, so no transparency > not good for rain-effect.
rain-shader: take a look at the plain used in the "rain"-posteffect, should be easy to declare it as decal.