I'm looking for a decent filtering program to add some flare to my pics. I take lots of shots of the trucks we do at my shop and I'd like to add a little something to them prior to publishing them on our Facebook page. All files are uploaded to an iMac prior to going on the page. Would like something that gives a few more options than iPhoto.

I'm probably looking for a free download or fairly cheap. Up to $50ish I could justify. Maybe I'm asking for too much.

Any idea?