I'm trying to create a nature scene with some plants which require alpha-masked images for the leaves. But whenever I UV unwrap them, the objects get coloured pink.
Make sure the Cycles Renderer is set as the render engine.
A pink color in texture view means, that there are missing images. You probably moved your Blender file to another directory or changed paths of image textures.
If the source path is not found, the message "Can't Load Image" will be displayed. Click on the folder icon to locate your image file (marked green).