In some cases, you may be trying to paste an image from your clipboard into the picture or filter areas of the Terrain Editor. This can not be done if the image is an 8 bit grayscale image. Bryce will only accept images from the clipboard that are in 24 bit or 32 bit color modes. To solve this problem, paste the 8 bit image in a 2D application and convert it to an RGB image of at least 24 bit color, even if it is just grayscale. Then copy the image back to your clipboard and try pasting into the terrain editor under the picture option.