No the beheading took place long after the prisoner abuse photos were exposed.
Reading between the lines there is also a lot more to this particular episode than meets the eye. In the Daily Mail it reported that he stopped off in israel on his way to Iraq(for what?). And shortly before his capture he was arrested by the iraqi police ( again for what?) and then handed over to the fbi who detained and interviewed him for quite some time ( again we do not know why they had such an interest in him).
No doubt more information will filter out in due course, but if he was up to something, I have no doubt that that information could well have leaked out, probably via the iraqi police and this may not have been purely random