All these were rendered with The GIMP’s Flame filter (Filters -> Render -> Nature -> Flame…). They look very cool and could be used as wallpaper images.
Enjoy!
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wow the last one look pretty funky! I like it 
Neat. Good job of finding the right level of complexity for the shapes. I’ve done quite a few of those; they tend to get a little boring after a while, the same basic flames… what makes it really fun is to use the gimp or some other program to do fun things with the results of the flame plugin. shameless self-promotion you can see some of the things I’ve done along these lines here… used the Windows program Dogwaffle for the matrix-esque number layers.
They look cool! I might just use them for my wallpaper on my PC… Nah.