I think the key is polite complaints and suggestions rather than beratements and demands I agree totally. I guess it all comes down to good manners on all sides. If you make a texture for something that isn't available anymore, you ask the original supplier if he might consider putting it back up again for a while (or letting you put it up on your site). If there's a problem, you gently point out that there's a mistake in the links or the way the files are set up. It's all just good manners, right?