Oh right, "thread painting"? Thanks for the links!
This is a tutorial on it, a lot of people seem to refer to it as "free-motion machine embroidery" or "freehand machine embroidery":
So there isn't really a place on Craftster (yet) for free-motion machine embroidery? Maybe I should ask the moderators to create one, if this ain't the place.
Starting tonight! W00t!! Inspired by all the many beautiful examples on etsy and flickr!
ETA: The Nancy Price thread painting links are very interesting, they show how one can do 3D type appliques, but the instructions can just as easily apply to "line art".
I went over to the Quilting section of Craftster, wasn't much on free-motion machine embroidery, but I found this advice from kellen46:
Uneven stitch lengths in your quilting is a result of uneven feeding the fabric under the needle. You tend to go faster on the straightways and so get bigger stitches, you go slower on the curves so get the smaller ones. Free motion is like trying pat your head and rub your tummy at the same time. Your machine needs to go fast as can be but your hands need to go slow and steady. If you have a machine that can go to slower speed it might help you in learning to machine quilt. If not work on setting your sewing speed with your foot peddle. One other reason you stitching is uneven may be that you are too tense when you sew, this leads to jerky movement, you will get spikeys rather than curvies, and your needle will "Jump". You will get better as you do more, it is a matter of practice, practice, practice.
Also this link to a video: http://crazymomquilts.blogspot.com/2008/03/free-motion-quilting.html
And a link to a flickr discussion: http://www.flickr.com/groups/quilts/discuss/72157603769221154/
This is my first attempt at free-motion machine embroidery an hour ago (complete with thread snags and breakages, oh my!)
I am SO excited!!!
Right, signing off on this thread. Hope the OP and anyone else finds the info in this comment useful!