With an electronic cutter, like the Silhouette Cameo, stencils are cheap and easy to make.
I make reusable stencils and masks from translucent plastic subject dividers.
Mine are quite old and were bought in the US, very similar to these, they are softer and less brittle than the polypropylene 'popper'-ed wallets. The slight colouration is useful as they show up on your cutting mat.
They can be used with texture paste, spays, mists or with ink blending tools and stamping ink.
If you have a Silhouette cutter and use the Silhouette Online Store you can download and cut designs very easily; just search 'background', 'overlay', 'mask', 'doilie' or 'doily'.
This one is the Wood Pattern Background by Tanya Batrak, design #49120. I think it works equally well for water as in my Origami Fish project.
This one is Flower Scolloped Circle Simplified by Samantha Walker design #4836.
Other favourites of mine are Antique Doily by Lori Whitlock design #15658 and Scattered Raindrops background by Loni Stevens, design #26878.
I designed this set myself, but it very similar to the Honeycomb Screen by Jennifer Wambach design #56061. It shows how you can easily adapt the design to mask out a portion of the stencil. Folks have been asking me for cut settings and a video - I'll have to get back to you on that!