Because i know your a render artist i'm going to suggest some heavy work.
-Shading
Using a burn tool you can darken areas of the character to fit the surrounding area, and add a more dramatic appearance. This would ofcoarse mean you would have to do it for every frame. Since it's in motion you might want to try to get teh shading to move accordingly.
-Particle effect
Or something of the nature, so you can have the appearance he's being drenched in the rain. I'm imagining wild clusters of particles graced in an aura of white glow, just like what they did for Solid Snake in Metal Gear Solid Sons of Liberty on the outer oil tanker stage. This activity should be as rapid as the rain is.
-Timing
When it inhales, you can make it slow to a stop, and when it exhales it drops then bounces back up into frame. Doing the slow in and out late in the cycle will help prevent any choppy appearences in the re-animation.
-Background Drizzle
A kind of cloudy feild used in the background to complement the layer of rain you have there. Another layer of shorter lines behind the character might work if the colours of the rain itself can speak depth, as backgrounds in large outdoor scenes are usually brighter than closer objects. I can only imagine when it's raining the background would be darker. So a kind of misty dusk at the right tone may pay off, i don't think it would need to be animated either.
-Masking
A slight tinge of reds and browns on the character to bring it more into the scene, It would make it look more in set rather bering in a studio. Too much colouring would wreck it and you may not have to do this after sharing it. I just think the characters appearance is too bright. I assume your avatar is something you lit up yourself so reach for the brilliance best you can for this.
I'll just leave it at that cause that is alot of things for a signature. I would nail you for the surfaces crossing over one another on the left shoulder plate into the bicep, but that isn't your fault. If you do fix that it should buy you some clone stamp bragging rights for awhile.
