Hello!

You cannot "convert" a photo to a "mat". However, you can use your photos to set up tiled materials. To do this, you need to first turn your images into seamlessly tileable ones. This can be done in a number of programs, for example photoshop and there are also some specialized ones that make it easier (for example Genetica). Once you have a seamless texture tile, you can load it into vue and use the material editor to set up highlights, bump, etc. and then save it as a .mat for use on any model.

It is very important, that your photos are free of shadows, obvious highlights and other artifacts. Otherwise they will make poor textures.

Ciao

TD