The attached script (see below) is based on Michael's grungy photo tutorial located here: viewtopic.php?f=10&t=137 Give it a try and let me know what you think. You choose the Filter Layer Color and whether or not to merge the layers. Unfortunately, the levels can't be set interactively so I had to plug in the tutorial values and they are set automatically.

The script is located below in a zip file. Download the zip file, double-click to open, and copy/paste the scm file in your GIMP scripts folder, refresh your scripts and go to Filters > Decor > Grungy Photo...

Let me know if you have any suggestions for improvement or questions.

Art

I will need to do michael's tutorial before I can really judge differences in the script and the tut. Here's my go at the script.

Here's a link to the original image.
http://www.quickcashauto.com/Car-Facts/images/Rust-Car.jpg

Cool script, Art!

My results

For some reason your modified pix is missing.

Fixed the link.

That is a real cool script thanks fencepost! =)

This has possibilities ... this photo is 105 years old.

WOW! ... that's an old photo =)