<t>In the past I have used GIMP which is quite a bit more tedious. Also used Blender one point many years ago, and again very tedious. And that is kind of the theme for most other option. Inkscape looks interesting but I run Linux, only, so it requires using it with WINE and sometimes that is easy ...

<t>3D is nice an all, but at the end of the day the contractor can't use any of it. He will be polite and take your "layout", while thinking he would like to strangle you. He will go to his office and place that "layout" in file 13, and in about a week or two with come back with something he hand ...