This may have been done before but i can't find it on here

RAWR!

Default your Colours (D)
Open your new Document at about 400 x 400
Filter>Render>Clouds
Filter>Render>Lighting Effects
Change the Lighting Effect Colours to Pure Orange And Pure Red
Omni
Play around with your settings until you get a flamy feel
Your done!

It should look something like this:



Post up your Results!