How to Make Sparkle Textures
*This tut is for GIMP. Since it uses the Paths tool and a GIMP-specific brush, it may not be translatable to other programs.
Requested by
wunderkind_lucy and
narniacmr .
1. Start with a plain black image. It can be any size you want, but the tutorial is going to assume you’ve got a 100x100 image.
2. Select your Paintbrush tool and use these settings:

Yes, you have to use the Sparks brush.
*Note on scale: I often change the scale several times when making a single texture. As you can see, this one uses several different brush sizes:

But most of the time I scale it to 0.1 or 0.2. Here I put it halfway between the two.
3. Now make a new transparent layer. (Layer>New Layer>Transparency).
4. Select the Paths tool. Use it to make a zig-zag or spiral pattern like this:

Hit ‘Stroke Path’. Select ‘Stroke with a paint tool’ and set it to Paintbrush. Check ‘Emulate brush dynamics’.
*Note on paths: Do NOT select any other tools before you’ve finished designing and stroking the path. Because if you, for instance, click on the Move tool, your path will disappear. (Bye-bye path! *sadface*) If this happens, it’s okay to cry, because you will have to start all over with your path. :O (This actually happened to me as I was writing this tut.)
Mine looks like this:

5. Sometimes, the Path doesn’t quite end up with quite enough sparkle. If that’s the case, select your Paintbrush tool and add some sparkles wherever you wish.
6. Now Desaturate the Paths layer (Colours>Desaturate>Luminosity). I usually choose 'Luminosity' for this since I prefer to have the sparkles almost white rather than a shade of grey, but ‘Lightness’ and ‘Average’ work just as well. Mine:

7. Now, you obviously want to change the colour of your sparkles. I mean, white sparkles are nice if you like that sort of thing, but we want some rainbows or something here, right? Yes, indeed! You can do this any number of ways. If you just want your sparkles one colour, like I did here:

You can Colourize or Colourify it (both under the Colours menu. Make sure you have your transparent layer selected!) But, if you want to have to have more than one colour, like these:

You need to use the Gradient tool. For rainbow colours, make your foreground colour red and your background colour purple, and choose the 'FG to BG (HSV counter-clockwise)' gradient:

Make sure the Mode is set to ‘Colour’! Of course, you can use any colours and/or gradients you like. Mine now looks like this:

8. If your sparkles aren’t bright enough for you liking, you can brighten them by duplicating the sparkle layer or by fiddling with the Brightness-Contrast. Mine:

I duplicated it twice and lowered the opacity of the top layer to 40%. And looka there! It don’t look half bad - even though I used a spectacularly unimaginative path!
Sparkle textures are some of my favourites to make, so I hope this is helpful and I hope you have fun! If you need any help or you think I should clarify something, let me know!