mini tutorial describing how I correct textures (using Photoshop or similar) to be used in a 3d program like 3d Studio Max:
-duplicate the photo layer
-guassian blur the hell out of the duplicate (high radius), eye drop somewhere in that image with a 101x101 average eye dropper to get an average colour
-fill a new layer with that colour (you can delete the blurred layer now), call it base layer
-turn off the 'base' layer and go back to the background, duplicate it and move it up to the top of the stack
-go to filters/other/high pass and experiment with the radius slider till you get a good detail/uniformity of colour balance (100 worked for me)
-immediately go to edit/fade high pass, change the mode to luminosity and keep it at 100
-name this layer 'high pass' and set it to multiply
-add a levels adjustment layer to 'high pass', tell it to use previous layer as clipping mask and compress the levels (move black point up and white point down) till it resembles the original texture
-if it looks good but is too dark add a levels adjustment layer to 'base' and make it lighter.
-now it is ready to make into a seamless texture...