I don't have a sample of this technique yet, I just thought of it this morning, but it should work and it should be extremely simple. Just time consuming like all good things are. :-D
Starting with background papers, such as Kara's Montague Paper Pack, available HERE.
Load one of the papers to a transparent background and again using either the marquee tool or the lasso tool, simply create squares, rectangles or triangles from these papers and save them as individual pngs. This would be easier if you use the grid. Make a bunch of shapes, in various colors and if the papers you are working with are not textured, add some! Play with the opacity and filters also. Once you have a bunch of these shapes to work with, simply apply them to a black background in a pattern of your choice, or create one of your own! Fun fun fun!
Here's another suggestion: Google stained glass, not the patterns this time, but the actual glass. Notice the beautiful textures of these various wonders, the shine, the opacity, they would make beautiful backgrounds too, or pieces for your creations. You can use these photos of glass or you can take it another step and create these, digitally! Yes you can! I will leave you to ponder this and if you are daring-give it a try! Don't forget to use all the digital tools at your disposal. :-D