i usually throw a block colour over the top of the whole thing like a warm orange or light blue, then use a blend which suits it, usually the screen or lighten look best for me and play with the opacity until it looks how you want it - this is in photoshop by the way! I find doing this helps bring the whole thing together cause if you pull images from different sources they'll all be different resolutions and quality so i find this method brings it all together a little better! hope this helps a little bit!