a few folks have mentioned they would like to see a little texture tutorial and I've gotten a few questions on how I did my textures for maps like Radigast and others. Well, I slapped a mini overview together and I hope it will explain some stuff. The overview assumes you are using Photoshop, but any bitmap editing software with layers and masks should do the trick.
Step 1: get a map.
I made this one for the purposes of this tutorial ... it's not perfect, since it's in colour and not black and white, but I got carried away at some point while drawing it ...
Step 2: add your texture shots (scans of old paper, photos of rusty metal sheets, cracked paint, dirt, plaster, sand ... whatever. Main thing is, it's more or less consistent and not too contrasting - you don't want it messing with your content)
Here I've duplicated a layer of cracked paint for the start. In the Layers panel you set the blending of each layer. Usually I'll use multiply and overlay layers, sometimes a screen layer as well. Each of the blending modes does it's own thing (and I suggest you play around with them) - but basically multiply multiplies the pixel values (darkening everything), screen divides the pixel values (basically making things lighter) and overlay does both at the same time, making highlights and shadows strongers (dark values become darker, light values lighter). The other blend modes aren't *that* useful to me, but ... whatever you like. I suggest a tutorial like this.
Why multiple layers? Because just a single multiply layer will darken your map too much (for my taste), while a single screen layer will lighten it too much. I duplicate AT LEAST the main texture (the one that will be the most visible), that way I can control what looks darker and what looks lighter, while not affecting the look and continuity of the texture itself.
Also, don't forget to adjust levels, hue, saturation and other things for your texture layers. Just fool around. They're replaceable, after all! All these settings are hiding in the Image->Adjustments-> menu (and elsewhere too).
That's the menu. Fool around. Use Ctrl+Z now and again.
But ... this by itself doesn't do enough.
Step 3: Masking your textures
Add a mask to EVERY ONE of your textures.
Now to work. Click on the mask. The white area lets everything through. When the mask is black it blocks everything. Get the paintbrush tool and press "D" giving you your basic black and white brush. Get a nice, big, rough brush with soft-ish edges (from 200 pixels wide on up). Set it to a low opacity and flow (fiddle around for a setting you're comfortable with - it depends on the texture, the image below, your preferences, etc.) and start making parts of your map less textured by painting around. What you're doing is masking (hiding) bits of texture to let you manually choose which parts of the map will shine through "clean" and "unsullied" and which will be grimed and hard to see - this way you can keep texts legible while doing horrible stuff to most of the map. Press "X" now and again to switch from black to white (X swaps your background and foreground colour in PS) if you have to erase your mask.
Now do this for every texture layer. I sometimes hide the layers I'm not working on, so I can see what I'm doing more clearly. Try to avoid sharp edges, as they'll be too visible and spoil the effect.
Step 4: Enjoy your artwork
Here you can see I used 5 texture layers - 1 paper, 2 cracked paint (one heavily desaturated) and 2 rusted iron textures. At bottom are your two friends - the adjustment layer tool and the masking tool. Each texture layer has its own mask that I doodled in. Obviously, I adjusted the opacity of the layers as needed as well.
Here is the final, textured version of the starting map:
Textures don't work the same way on different maps, so each one is best done on its own. Here I've applied the exact same texturing to a different map:
And, it could use some work.
Step 4: The End!