In the paper here, I collaged on some birdlike tissue shapes, but you can make yours with or without any shapes you like! Begin with white or any other very light-colored tissue paper, the cheaper the better. With added shapes or not, place the sheet on waxed paper or freezer paper, and brush the up-side with fluid acrylic medium (I like gloss best for this).
When that's dry, peel up the sheet, flip it over, and apply a coat of the fluid medium on that side, too. When dry--and if you haven't used dark tissue colors--the page should be quite translucent.