Thank you all for the great comments and interesting guesses! :) I'm sorry I don't get back to each and everyone of you with thanks but I'm really limited in my online time atm. I just pop in a few minutes here and there.
The best guess comes from Andy aka co2metal. It's indeed a crumbled up black wall chart piece from a U2 poster that my wife put in the trash and my son started to massacre... ^_^ I did a few experiments on different ways of crumbling it and went straight for my camera as I realized it looked pretty cool...
The plain black and offwhite (and yellowish) original is still quite nice IMHO but I guessed it was better to post more colorful versions here so I played around with the color adjustments for some time and picked two or three out of perhaps ten versions.
I guess so. My dictionary say: "transubstantiation |?trans?b?stan ch ??? sh ?n| noun Christian Theology (esp. in the Roman Catholic Church) the conversion of the substance of the Eucharistic elements into the body and blood of Christ at consecration, only the appearances of bread and wine still remaining. • formal a change in the form or substance of something." I was thinking more of the latter though.