I love Rosco materials! Send for their catalog- there are so many items that are primarily intended for cinamatography that are great for still work as well. They have all kinds of reflective and diffusion materials, each with its own special properties.
As far as gelling the background, here is what I have observed at my studio. If you want a textured or painted background that is best for using gels, it is best to find one that is neutral gray. If you have a multi colored background you can run into problems with "dead spots". As an example- I have a background that has delicate touches of pink- it picks up nicely on pink and pastel flowers in bridal portraiture. If I was to use a green gel it would neutralize the pink areas and create muddy spots. With the gray background I have used more that one gel on different lamp heads or on different parts of the same lamp head to create interesting variations in color mass.
Many of the Rosco colors are available in various densities or light transmissions- some have built in diffusion lawyers so different levels of brightness and darkness in the background can be achieved without even changing power seatings if a wide range of outputs are not built in to you background light.
Where textured and painted backgrounds are concerned, I prefer ones with good contrast- different degrees of softening can be had by increasing or reducing depth of field or by varying the distance form the subject to the background.
Even in low key work, I prefer some subtle detail in the background rather than a jet black effect, I like to use my background to provide color or tonal mass. I find that this gives my images more separation and dimensionality. Sometimes jet black backgrounds take on the appearance of a cut and paste job.
Just some suggestions
Ed