Lights... I might know how to fix the squares.... in gimp ALWAYS and I mean it ALWAYS save 2 copys when you finish a .xcf and a .png (Xcf can keep the layers so you can re edit later) now just sharpen the squares alot then try smudge and burn and maybe it will give you the same effect.... and if you ever need some resources Stocks/renders/c4ds/overlays/brushes/scripts/ect I can help ya!
Here for renders. www.planetrenders.net
Here fro brushes www.Deviantart.com
Here for Scripts www.Google.com (LMAO I know just google GIMP scripts!)
and
Here for GREAT Tuts. www.Gimpusers.com
http://www.gimpusers.com/tutorials/smelting-text-bloody-text.html <---- Cool easy tut for blood text!
(this is what the text will look like)