Image_lib is quite inconvenient in its current state.

[eluser]Crimp[/eluser]
The quality of GD is amazingly bad compared to GD2. Not only for thumbs. Run php info on your server and check which version is available. Set the GD2 in configs. I'd also echo the recommendation of simply storing filenames in the db. It's foolproof (hence perfect for me) and also allows for easy use of encryption to make direct access to files more difficult.