Hey, guys, I finally made a background tutorial ! ^^ ( sorry, it is a little messy) download for full view!
You can make this kind of background in 20 min ,I think .
I don't wrote a lot of description because you just need to mix your colors and add details with your pen
STEP 4: You need to select your background, "copy", "edit", and "past" <== and now you can change the opacity of this new (multiply) layer
</span>All was done on a 1 layer, except the final step (add 1 multiply layer and 1 overlay layer)
<== I think it's really important for your colors
Done with Paint Tool Sai ( 35min)