You can apply bitmap images to your models as texture maps. For example, when you want to apply a texture map that was created using another paint application and then continue painting or sculpting the model using it as a reference while working in Mudbox.
All paint/texture maps are managed using the Layers window.
The image is applied to the assigned material on the model based on the UV texture coordinates and is loaded as a Diffuse paint channel layer. For more information on UV texture coordinates, see UVs overview.
Importing a texture map in this manner applies to the selected channel for the assigned material. If many objects in the 3D View share the same material, the texture map will appear on those objects as well. If this is not desired, simply assign a different material to the object before importing the texture map as a paint layer.