I was literally scanning my entire PC yesterday for an alternative. timThumb reminded me of an alternative that a Wordpress theme I have, uses. It's basically SO much more feature rich, easier to use/install, configure, etc. And I found it earlier today. Have a look:
http://phpthumb.sourceforge.net/

Yep, can work with remote, local, or database images. Can watermark your thumbnails. And of course, a huge array of all sorts of filters. Have a look.

I'll see if I can modify timthumb to support remote images. Though am not so confident, but hey, I'll give it a shot anyway.