There are lots of different banners used in photo sessions. I've noticed a huge variety. I have made a couple in the past. Then I saw some using simple muslin and I decided to make a few of those as well. I'm sorry that these are not original ideas- they are copies of what I have seen around the web- with directions on how to make them for your photo prop stash.
The first banner is made by cutting out fourteen triangles. Then place two together and sew them on top of each other with a simple zig zag stitch (just making them thicker so that they'll hang better).
The "string" is made by cutting strips that are two inches wide. Fold in half and zig zag the length of your "string". Place triangles onto string and zig zag in place. Leave the edges raw, show the stitching- it all adds texture.
The gathered muslin strip is made by cutting a strip of fabric three inches wide. Sew a large width straight basting stitch down the middle, and then again one fourth inch from previous row of stitching- do not back stitch. Then pull end strings to gather. When it is a "ruffled" as you like, sew down the middle again using a small straight stitch. Drape as needed.
Now, I really ought to quit playing with props and start learning how to take photos with some real people!