First of all, we need a heightmap. For this tutorial, I'll make a valley-like landscape. Here is a small version of the heightmap I will be using:

Here is the heightmap. The dark area makes room for a nice water surface when we get there.

The original heightmap is 750x750 pixels, but when you use this methode, you can of course use a larger image to get more detail.

Now, second, we need the map. To make this, load the heightmap into your favourite paint program, and start painting the texture. It's important that you know what the grayscale image represents here. The darker colours represent the lower areas in your landscape, while the lighter colours represent the higher areas. In our case, this means that we will have a landscape that looks like a valley, and has a "lake" in the middle, and with some high peaks around. Of course, in a real job, this one wouldn't be very good. But for this turorial, it's ok.

Now, in my case, I use Photoshop 3.0.4, which has the possibilty of using layers. This means that I can load the grayscale image, add a new layer, and paint on that:

The Adobe Photoshop work area. Note that I have just begun on the paint process.

Note here, that the texture map this example produces will also be in the size 750x750 pixels. For higher detail, increase the map-size. You can with the use of layers also see how your map corresponds to the actual landscape. Just turn down the transparency in the layer control, and you will see what's in the next layer. You can use a soft brush to do the general painting and most of the details, but you should also use a harder brush. To get a more grainy look, you can use noise. Other enhancing effects are for instance adding relief with KPT Convolver. Here is the painted map (a small version of it):

Here is the texture. This one is very low on detalis, and the colours could be different. But it will do for this example.

Now you have the texture as well as the heightmap. It's time to start 3D Studio MAX. Now go through the steps as shown in the landscape tutorial if you don't know how to do it. If you do, you can go on with the next step, which is applying the texture to the landscape. I asume you know how to make a material, so I'll leave that to you. Just load the texture you painted into the diffuse slot. Also, you can add bump and things like that, but I won't do that here. After you have made the landscape and the material, apply the material to your landscape, and add a planar map to it. This map should be aligned so it fits to the alignment of the displace map. Here is the landscape seen through the Perspective viewport with the map visible:

I also took the liberty of adding a noise modifier to the mesh.

And there you have it. The map and the landscape in this tutorial might not be the most professional or well made, but it illustrates a methode of texturing a landscape. If you want more detail to the landscape, you can increase the map-size, and paint more accurate details. This is of course not the only way to make textures for landscapes, but it's a quick and easy way if you have Photoshop and MAX. With more work on both the landscape and the map, this could turn out pretty good. Now I would only have to add some water in there, and render the thing. Good luck!