Image Resolution

How much resolution?

1. The first thing to keep in mind when working with images in Photoshop for 3D imaging is keep the DPI at 72 to start with. There is no good reason to raise it any higher. If you want or need higher details in your map, up the image size (width and height) also known as map resolution. If you know the map will be used in any close-up, you may want to consider a higer resolution.
2. What is the goal of this map? Gaming? TV? Film? Knowing what the ultimate goal of this map will help you determine how much resolution you will need.
3. Keep the maps square is resolution. Why? Because numbers like 2, 4, 8, 16, 32, 64, 128, 256, 512 and so on are square numbers, these values render faster.
4. Game maps vary anywhere between 64x64 up to 512x512 currently. The next generation of game maps will be much heavier.
5. TV and film resolutions can be anything you like. Again, if you keep the image maps square, it will render faster. If you have a character has a close-up, you might to consider a high resolution somewhere around 768x768, 1024x1024, 2048x2048 and so on. I have yet to use a map that has gone beyond 2048x2048. On the other hand, if an object in the distant background that will be blurred out, you will not need that much resolution. In fact, I might consider using a procedural shader with minimal color information.