I help you out with this, but Blender is for making .dts shapes, not for interiors.
You changed the material name, but you didn't change the texture name, or select the image file to use for the texture.
Step by step instructions.
1. Open the file.
2. In the buttons window, find where it says Tex.001. Rename it to island.
3. In the right side of the buttons window, press the load button.
4. Navigate to where the texture file is, select the texture, and click SELECT IMAGE.
5. Now export.
You may need to mess around with the 'map input' and 'map to' setting. I can't help you there, texturing is something I'm not really good at.