I always wanted to give GIMP a shot because I read a lot about it on deviantart..So, here goes nothing...This is the first sig I made
1-> Fire in the background made rendering plasma(seed=randomseed;turbulance=6.0)
2-> Desaturated the plasma and adjusted the color balance to get the desired flame effects.
3->created new layer added a few grunges and light effects to get the background..
That is all, rest is just using brushes and little filters(ripple) to actually create a little wavy motion on the image..but I am not sure if i succeeded there....