I'm writing it in Paint Shop Pro, but it should be translatable to other graphics programs as well. You can literally make a mask out of anything...Preset Shapes, Dingbat fonts, Photographs, Word Art, brushes, outside graphics filters, tubes, scrap elements, etc. Please keep in mind, though, that most artists, photographers, and scrap kit makers do NOT allow you to make masks/brushes with their work, so you should make sure of the Terms of Use for whatever you are wanting to use. If in doubt, ask the artist/maker for permission. However, if you are going to use tubes, scraps, or photographs, it is always best to use those items that you have made yourself.
First, how do masks work? They work on a grey scale with black blocking out all the color from the background you are working on to white which allows all the color to show through. Here is a very simple mask I made to show how varying shades of black/grey/white show on a background.
Note: There is actually a white rectangle at the end of the grey ones and at the beginning of the blue ones.
So, here are the instructions I used to make a simple heart mask. This will make the exact same mask I have at the bottom of the post.
Supplies
Paint Shop Pro (I used version 9, but it should work in other versions.)
Mura's Meister Copies
1. Open a new canvas 800 x 800 and flood fill it black.
2. With your preset shape tool draw out a small vector shape in the color white. I used a heart.
3. Objects>Align>Center in Canvas
4. Apply Mura's Meister Copies with the following settings.
6. Repeat twice more, always duplicating and resizing the smaller layer. You should have 4 layers of heart circles.
7. Hide your background layer and merge visible.
8. Adjust>Softness>Soft Focus with the following settings.
9. Crop your canvas to your liking.
10. Unhide your black background layer and save as a JPEG. This is my finished project. You can also embellish with brushes, sparkles or other shapes.