I was about to make a new user texture, for a brick facade. I was just wondering, because in the image library of Dietrichs GIF, there are both bmp, png and in the material database under user textures there are tiled 1x1 m, stretch and stretch_grey. If I remember right, the tiled are for textures that needs repetition for bigger surfaces, while stretch are for surfaces that has a specific size.
But can one else from that, choose freely between bmp, png, stretch, stretch_grey etc.??