Heh. Nice one!

One of the main problems with doing this type of work is lighting. One filthy-rich friend Mister Woods is clearly being lit from the right-hand side, and quite low down (it must have been late in the afternoon by the time he won whatever it is he's winning there). That doesn't match the King or his guitar, though his enormous head is cartoon-like enough that it doesn't really matter in that case.
As for stitching together bits of image, Xara's pretty good at that, with its bitmap handling and feathering. The extended transparency effects can also be used to recolour one photo to fit another. It's a shame there's no dynamic bitmap-style filter fills though, that might allow one to make a shape blur things behind it, eg. to match focus. Instead one is limited to the plug-in bitmap effects.

Some people would probably try to do effects like this in a bitmap editing package like Photoshop. But I find them very cumbersome compared to a good vector app like Xara.