First I made the light rays. Did that by duplicating the background layer, deleteing everything around the windows, then I tweaked contrast and brightness and added motion blur to get the effect. later I did some minor alterations on them. =)
step 2 of 5
Since the original image had light coming from the other side to, I pained over some shadows. It's a new layer, mode on 'darken', around 75% transparency. This is what the layer looks like, tho later I added more some shadows too.
step 3 of 5
Some more alterations to the light rays, added more shadows, and also the shadow of chandelier (in the rays). Some places burned some dodged etc etc.
step 4 of 5
Some final touches like sharpness and the dust. Dust is a black layer with noise put on lighten (or was it overlay...?), and erased the unwanted places.
step 5 of 5
And that's it! Then I made some variations with various cooling filters, warming filters, underwater filters etc etc, and eventually decided to use the warming filter (a yellowish-orange colour). Hope you like! =)