If you like creating pictures with tools on the internet, check out Flame.  Peter Blaskovic, the site's creator writes

"Flame is a painting program, it belongs to my 'I am Artist' experimental project. I think with tools which inspires you, everyone can be an artist. You can try it here, change different brush settings and paint your own flame paintings. When you change background from black to white, palette changes from additive to substactive and the feeling of the painting is very different. It's not easy to explain all brush parameters, so I leave this for your experimentation."

Here's a screen shot of Flame:

The secret is in the tiny controls at the bottom of the screen:

Use your mouse to slide the bars to the left and right to vary the texture, color, opacity, effect, etc., of the lines you draw with your mouse on the canvass. You also control the lines you create by varying the speed and curve of your mouse movements. Below the painting area is a long list of the tools you can use and regulate to create your picture.

The easiest way to save your picture is with a screen shot.  (The "save" button didn't work for me, but I was using Google Chrome as my web browser.)