What I use for backgrounds is most of the time Daz-cyclorama, which uses real photo's to fill the scene, I rarely use any postworking to improve my renders. Only the last two renders i've made I used a photofilter to improve the lighting, but honestly speaking I'm not so glad with the results, the other reason why I use postworking is to remove renderartifacts that sometimes occur, and poketroughs in clothing. but besides that I'm not such a skilled postworker, although I'm learning day by day.
I think that if you do enough preworking, like setting up your scene right, getting or making the right shaders and setting up a good lightingsystem, applying the right rendersetting, you don't need postworking.
And doing dozens and dozens prerenders of course before you get it right...

Bopper.

-How can you improve things when you don't make mistakes?