I made these for a fellow airplane nut's birthday party. I made all of these from pictures I found online and this was my first use of Inkscape. Fantastic program!
I was amazed how easy it could be to make a cookie cutter out of any old image.
1) Find an image (preferably with most of the contrast between the object and its background: silhouettes are ideal).
2) Import it to Inkscape and click Path -> Trace Bitmap. The defaults worked great for me, but it can help to adjust the threshold on the brightness cutoff.
3) Once you click OK, a spline version of the image will be layered on top of it. I move this over so I can adjust it separately. Now you can go and tweak the splines as necessary to fix anything that won't work nicely as a cookie cutter.
4) Now I basically follow the DXF export instructions from: http://repraprip.blogspot.com/2011/05/inkscape-to-openscad-dxf-tutorial.html. The summary is Object to Path, add some more points to the splines, then convert them all to straight edges and save as DXF.
5) Open cutter.scad and tweak the base module until the DXF is sized and oriented properly (the build platform is also displayed when compiled). Export, print, and eat entertaining cookies.